Spend more money on the amp or the pre-amp?

Nakamichi CA5 < $300 and PA5 < $500, can't think of any integrated < $800 can beat that combo

It depends. Do you you need a phono stage, tape loops, HT pass through, how many line level inputs.? Perhaps more importantly, how much power into what kind of impedance load do your speakers need in your room? Depending on the the answers to the above, you might find some power amps that are suitable for use with some fairly inexpensive passive pres.

Mostly great suggestions, but I would advise caution shopping for used or vintage equipment unless you are prepared to work on it yourself or pay a technician $85.00 an hour.  At the OP's price point, paying for repairs or upgrades is probably not an option.
Seems strange to say this on Audiogon's forum.  This is actually a great place to buy used equipment, as most sellers are audiophiles themselves and know the value and condition of what they are selling.  You will usually find good, fair deals.  When shopping on the open market, however, caveat emptor.

Spend it on the cables

I bought a Rotel RB-1552 MkII here for $300. It is dented on the top but sonically it is perfect. If you keep your eyes peeled and stay patient you can find great gear. The DC offset on mine is so low it's hard to measure, and it is quality gear. That would leave $500 for a preamp and you have a lot of options at that price point. If we knew more about your source and speakers we could recommend something more specific. Do you prefer tube or SS sound?