Since I didn't see any mention of weight in the OP, I'll assume that's an open-ended requirement...
First off, you don't make it clear what you mean by "designed for jazz," which could mean anything from a prewar Gibson EH-150 (or the aforementioned Epiphone "bandstand" combos) to a modeling rig that specializes in clean tones or anything in between, tube or solid state; that said, when it comes to a go-to amp this old guy favors "big-clean" tone: harmonically rich, loads of headroom, sufficient volume for any gig I'm likely to play (up to a 600-700 seat hall), and 12" or 15" speaker(s) to adequately reproduce that characteristic creamy low end in something larger than a small-club setting...
Inasmuch as the term "boutique" appears in your opening question, it's a pretty safe guess that you're prepared to spend whatever funds necessary to achieve your signature tone. Once again, a bit of clarification would be helpful: are you looking for the slight wooliness of prewar combos, classic '50s Bop-era warmth, the equally classic '60s tube-driven clarity exemplified by blackface Fender and blue-check Ampeg gear, '70s/80s first-generation solid-state clean (Roland JC, Polytone, Randall "orange/grey-panel" two-channel combos), "modern" Class-A tube tone, pre-2K MOSFET/JFET "tube wannabe," new-gen Class-D big-power featherweight, or a modeler that can call up all of the above (as well as a bunch we haven't touched on yet) at the push of a button? Needless to say. keep your artistic preferences in mind when you make your selection - IMO your choice of instruments (Heritage 575 and Guild Starfire III) suggest a broader-based approach, and since the amp is at least 50% of your final tone you'll need something that not only reflects your versatility, but accurately captures the tones you're hearing in your head and complements both guitars equally...
I don't know how much prior experience you have with electric guitar amps in general (and those that will serve you well as a "jazz amp" in particular), but in the grand scheme you can't go wrong with a classic medium-/high-power 1x12"/2x12"/1x15"
American-style tube combo - meaning 6V6/6L6/7027/6CA7 power section and American-voiced (Jensen, JBL, EV, Oxford, Utah, current Eminence Patriot series) speakers; although I've seen a couple guys press a Vox AC15 into service, British EQ/speakers don't really work well for jazz (one
possible exception - if you install an American replacement speaker - might be the 1x12" VoxAC30S1 that recently received a $200 factory-authorized price drop). Thankfully Fender has reissued their blackface Twin/Deluxe Reverb combos, and while the Twin is a real monster in terms of both volume and weight the Deluxe might be a viable choice - in fact, the best straight-ahead jazz tone I ever heard was a two-pickup Gibson Johnny Smith through a JBL-equipped Deluxe Reverb - especially if you need something versatile enough to cover both the Heritage and the Guild; if you still crave the big box but don't want to deal with the weight, the digital Tonemaster Twin comes in around ten pounds and $200 less than the all-tube Deluxe (FYI there's also a 23-pound Deluxe version), boasts all the key features of the tube Twin, and has a scalable power section (1W - 85W) that'll let you use it for any size gig as well as late-night practice...
If you're into vintage tube gear I'd recommend seeking out a good blue-check Ampeg Gemini II 30W 1x15" combo which, unlike their blackface Fender contemporaries, can still be had for well under $1K. These amps - along with the relatively rare 60W/2x12" B-12XT Portaflex (Ampeg's would-be "Twin-killer" and IMO one of the greatest - and least-appreciated - amps of all time) and iconic B-15 bass amp - were the mainstays of the New York studio/club scene in the 1960's; FYI the studio models were equipped with cylinder locks, with keys issued by AFM Local 802 only to A-list players (the origin of the "Key Club," New York's answer to the Funk Brothers and Wrecking Crew) - and if you're familiar with the period work of Tony Mottola, George Barnes, Al Caiola, Artie Ryerson, Hy White
et al. that's the tone you're hearing. Thing is, although these amps were conceived as jazz boxes (Ampeg founder/CEO Everett Hull hated rock music with a passion) they make excellent rock and country amps as well - I rented them (along with the baby-brother 1x12" Gemini I) back in the day for gigs where my '64 top-panel/non-reverb Rocket wouldn't cut it - and if you see yourself crossing over to the dark side on occasion (or plan to use a stompbox or two as sweetener) it's an ideal choice IMO. Absent the availability of a suitable example, I modified my first-generation "blue-light" Bugera V22 22W 1x12" to "Key Club" Ampeg tone-clone specs with an Eminence Swamp Thang speaker, a set of Soviet mil-spec replacement tubes, and a mild rebias (the current Infinium version is self-biasing); for a total investment of around $650 you can have a brand-new, all-tube rig that'll cover about 95%+ of the gigs you're likely to play, with tone that IME will open the eyes/ears (and furrow the brows
) of owners of boutique amps at two and three times the price - and if you still need more clean headroom the V55 55-watter will give it to you in spades, for about $50 more,,,
Good luck with your search...
