How much would I benefit from an amp upgrade?

My experience is in going from a BAT power amp for two channel to a NAD 763 paired with a M15 prepro for video. I kind of got out of Vinyl for a while but recently replaced the M15 with a NAD T175HD in order to be able to decode lossless codecs and 96k. The surprise for me was I think the two channel sound (which I thought would get worse) is actually better, perhaps due to the ability to use Audussy in a difficult room. I think I am getting the best sound ever from my vinyl now and I have been in this room for 20+ years and at one time had Appogees and a Krell.

Long story short, while I am probably giving up a bit to the BAT I am very happy with the sound. While not directly related to your equipment the point is that some relatively inexpensive power amps stack up quite well against some well regarded expensive equipment. On the other hand this rig is head and shoulders above a Yamaha receiver I used for a while when I first went into theater.

i agree regarding the krell s300i. can be found dirt cheap considering the power and HT features. had one for a while and enjoyed it. give one a try if you can. easy to flip used units if things don't work out.

I think you'd benefit a lot with a better amp. Right now there are a couple of new and demo Theta Intrepid 5 channel amps on Audiogon going for around $1,400. IMO, that's a no-brainer.

I am a big believer in 2-channel for 2-channel, it makes a very big difference. There are some great integrated amps with home theater pass-through which will serve your needs well. I have not heard the Krell 300i but that is on the right track.