What gives better sound and or control of the bass. Increasing the gain on the preamp or increasing the gain on the power amp. Either way would you hear difference in sound quality?
More gain = more noise.

Power amplifiers usually have fixed gain, about 20x, or 26 dB. They need this to translate the input voltages (often around 1-2 V) to the speaker voltages.

They may have adjustment pots in the input, but the gain of the circuit itself is fixed.
My power amps have a gain setting of either 26 or 32db. Is it better to have less gain on the power amp and no increase in gain on the preamp which has adjustments as well?

Some amps, like Channel Island D200 are sold in two gain versions. As they explain in D200 manual:
"Gain: 32db (for use with VPC, PLC or other passive preamplifiers) or 26db (for use with active preamplifiers)"
I would stay with lower gain if your preamp can deliver high enough level.  Building up the gain in preamp should result in higher signal to noise ratio than doing the same in power amp (noisier environment). It also minimizes effect of noise pickup from ICs.  Benchmark Media recommends lowest of three gain positions in my AHB2 amplifier.  They stated that "Most power amplifiers have far too much gain, and this degrades noise performance of the overall system".

There is no way to improve a recorded signal but 100 ways to make it worse. The best you can do is to amplify it in the preamp and to send it out with high gain to the amp.
What gives better sound

Utilize all of the sources gain don’t throw any away, is the best for the lowest noise, distortion and best sound.
If the source has enough gain direct to amp for the loudness you need, then you don’t need an active preamp with even more gain more noise and more distortion, a passive will be the best.

Quote from Nelson Pass

Nelson Pass,

We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.

Cheers George