Reel to reel deck directly to power amp ?

The other thing to keep in mind is the impedance match between the RtR output and Power amp input.

I run my RS1500 directly to the amps of my Beveridge Electrostats and the sound is fantastic!
Best of luck!

Yes, I was thinking about output/input match, but Ralph didn't mention there might be a problem. 
It should be fantastic sound, especially if you play good two track master tape dubs. But even recordings from vinyl will sound excellent. I make a lot of compilations, play them on my Nak 682ZX, I rarely play entire albums, I don't have many that I would want to play entirely and I don't enjoy moving the needle all the time. Nak recordings sound okay but far from vinyl, with reel to reel deck I will fix it, this should be very close.
When playing records thru deck by way of separate phono you can adjust volume with both volume control and recording level knobs. The you use tape monitor switch to listen to either deck or turntable. There may be a slight drop in the resolution compared to running phono signal to top level preamp instead of a deck, sure, but at the same time you will lose some resolution when playing deck connected to preamp as opposed to running it directly into power amps. Unless, of course, power amps have two inputs, so you could run deck directly and phono thru preamp and then to amps.
But in this case I would need to connect phono and deck directly, not thru preamp's tape-outs, to make best quality recordings from vinyl. Not too much work, though.
Anyway, I will start without preamp.
There is currently a pair of Clayton M70 monoblocks for sale on usaudiomart. That would work with my current and almost certainly future speakers. I keep my hands off credit cards, you won't find overall better amps for $2200, I guess.

There is a line level control for recording level and out put level to "pre-amp", not amp. The RS 1500 puts out a max signal of .775 volts, while a good pre puts out a max of 20 volts for the power amp.

From my point of view, this is a case of the blind leading the blind, and then running with it.

Yes, I was thinking about output/input match, but Ralph didn't mention there might be a problem.

With any pro audio or semi-pro reel to reel, you have a volume control to control output. On my Otari 8-channel, not so easily accessed as you have to put a screwdriver though a hole in a panel. But the two channel machines have a regular volume control and are typically set to at least +4 dbm at full volume (some might be at +10); either way that's more than plenty to clip any amplifier made, and the output is robust enough to drive any amplifier made.
IOW just do it :)
I of course prefer tubes, and used to do this with my Ampex 351 machine. It was a bit harder, as the volume controls were on each channel and so a bit harder to adjust. But more modern machines have made that bit easy.