Preamp Noob has a question

Please forgive my ignorance Mechans, but what are 6SN7s? Are those the tubes? I've never owned tube gear before. How often do tubes need replacing, and are they easy to obtain?

The OP asked for recommendations for a pre to power his existing amp section of integrated amp; if I understood the question properly.

Separates were necessary for high end audio, a long time ago; but not now. In reality, there is no such thing as "separates". The pre ckt that exists in the integrated, puts the pre in one box instead of two. The ultimate end is the same whether or not the ckt is in one box or two.

If you mate a top pre with the existing power amp section of the integrated, you will be wasting money because you will still get "crappy" sound.

Your most economical solution is to sell what you have, and get the best "integrated" you can with available funds.

I tend to agree with Orpheus -- if you like integrateds why not just upgrade to a better one? I know you're trying to improve your sound on the cheap, but while you may get some benefit from this you may end up not liking this preamp when you upgrade to a better amp (assuming that's where you'd be headed eventually).

I'd recommend saving your pennies to buy a significanly better integrated amp (say something like a Bryston B60R or similar), and in the meantime try to audition some integrateds and maybe even some preamps/amps in your system to see what you can expect from whatever upgrade you end up making. Best of luck in your search.

I tend to agree with several posters recommending a better integrated (Orpheus, Soix). To me it seems that you have 2 componentes holding you back (the preamp in the receiver and the amp in the receiver) and you are considering which one to upgrade. Unless you plan to upgrade 1 now and 1 later I think it would be best to upgrade them both now. A good integrated anywhere near the $2K mark (especially used) would seem to me to be better than either a great preamp + the Yamaha amp or the Yamaha pre section + a great amp.
Just my 2 cents especially considering I'm not familiar with your Yamaha or other gear

To answer your questions, yes 6SN7s, are tubes. They will last up to 10,000 hrs depending on the circuit, but you can figure about 5,000 in normal use. This particular tube is very easy to find since they are still currently produced. The better ones IMHO are the older ones, which among OS/NOS tubes, are probably the easiest to still find at reasonable prices. That pre only takes 2 of them.
I strongly agree with the posts recommending an upgrade to a better integrated. I got sidetracked by the conversation and your original request for a pre. Getting a better integrated amp makes alot of sense. If you are curious about an integrated tube amp, there are plenty, albeit Chinese, that you can afford, especially if you buy used. My personal predjudice is to go with tube gear, I love it and think the hassles are overstated.