Cheap Yamaha guitar---string advice
 

I play, mainly, steel-stringed acoustics, but I love, occasionally, to sit down with my cheap Yamaha C40. I finger-pick without nails, and I realise that limits volume.
I have been using D'Addario Pro Arte Normal Tension, but find the top three strings a little muddy. Of course, this could be the fault of the guitar.
Would the guitar benefit from the hard tension EJ46s?
Are there any other string recommendations?
Thank you in anticipation.

The hard tension Pro Arte strings may help with that. Before I found the Luthier Popular Supremes, I used exclusively Pro Arte Carbon Hard and Extra hard tension strings. I did that because I was looking for more punch, snap, quicker response, and volume. Note separation/articulation are part of that equation. Most nylon players have to experiment with different brands to really dial-in what they're looking for. But the Pro Arte strings are definitely one of the industry standards. Savarez is another. I'm not sure how much the premium brands like Hannabach are going to help you with a lower-end instrument, but that's your call. If you find yourself really getting sucked into the nylon world, I would definitely look to upgrade your instrument.

I used to own an old Yamaha classical and found that Savarez Alliance carbon strings got rid of any muddiness

I am on my first set of strings from the original on my C40, and do not use a plectrum like yourself. I was sold Ernesto Palla 2403 at the store and found they are very pure sounding strings, with higher volume and thinner E & B strings than the original.

It is definitely personal preference as I preferred the original over Ernesto Palla as the thinner strings would distort like you mentioned and this suited my playing style, so perhaps you might prefer the Ernesto. In the next couple of weeks I will try the Savarez.

Cheerio :D

Savarez 500 AJ HT Alliance trebles, Corum basses

My notes for a laminate top Takamine EC132C (tusq saddle):
robust, rounded, good volume, somewhat sweet, balanced, excellent 3rd string, excellent fretters, trebles progressively dry above 15th/16th fret