next step for my setup? advice appreciated

Hello,

I've been on an audiophile quest for the last 2 years and I'm at a standstill and would like advice as to my next piece of equipment. Here is a summary of my journey so far:

I started with a Yamaha Surround receiver through Boston Acoustics bookshelf speakers (CR77) with a Sony multi DVD player.

I've ended with older Rotel separates (RB980bx amp, RSP980 processor running 2.1 channel analog.) Oppo 980 dvd player for cds and movies, also itunes into airport express. Speakers are GR Research DIY kit (AV2) and a 10" canadian sub, the brand name escaping me currently.

I'm very happy with the sound and with the bang for the buck, but you know, grass is greener etc, so here are my questions:

-- would a tube buffer between pre and amp help? I see the Yaqin is fairly inexpensive, but also read diverse opinions.

-- how about a tube DAC? Would this vastly improve the Oppo and Itunes? Both are currently analog into the Rotel.

down the road, I'd like to explore tube amplification, but for now I'm considering building my own DAC or trying a tube buffer.

any thoughts appreciated

thanks

Steve Cuss

Obviously, the sound quality is up several notches now and I'm very happy