I suggest something like the RockMan.... with whatever ear buds or head phones you choose.
http://www.guitarcenter.com/Rockman/
It is likely that no amplifier will avoid annoying your neighbors, especially now that they are sensitized to the issue. You have to find a way to make acceptable sound in your
ears, not in your living room.
Consider a speaker with a typical sensitivity of 90 dB at one foot for 1 Watt of input power. Every doubling of power input raises the output sound levels by 3 decibels. You get the following sound pressure levels in your apartment (more or less depending on distance):
1 Watt = 90 dB
2 Watt = 93 dB
4 Watt = 96 dB
8 Watt = 99 dB
16 Watt = 102 dB
32 Watt = 105 dB
64 Watt = 108 dB
100 Watt = 110 dB
Since most apartment walls barely stop 40 dB of speech sound (and even less for amplified music) you are creating significant sound levels in your neighbor's unit regardless of how low you set your amp. Sorry -- blame physics, not me.