I feel that a clean 600 that is original is worth about $175.00-$250.00. Prices on EBAY tend to be in the same bracket...but you will see some creep in at about $150.00, and extremely near mint examples will of course be over $275.00.
You also can convert a 600 to MPX stereo with the outboard Fisher MPX-100 adapter, but even a ratty MPX-100 will cost you about $175.00 these days.
There are usually Alnico Jensen drivers in Fisher consoles (P12Q's, P8R's, etc)....so if you decide to break one up, you usually recoup some of your money selling the Jensens to guitar guys- since most of them are terrible for hi fidelity use.
I hate to break up a console...but the hard truth is that almost nobody has room for them or even wants them these days. I have attempted to give away almost perfect Fisher consoles to people (on the condition that they keep them intact since I do not have the room for one) and everyone has been honest with me and told me that if I did not break it up- they would be the one to do so. The "Boss" will only allow a Fisher President in the house (in a Danish Modern cabinet) and since the President cost anywhere from $2500-$5000 in 1955-1964, I don't think I am finding one soon.
Fisher also usually modified the console units with .0047mfd (vs .047) coupling caps to filter out rumble from that Garrard RC-88. So when rebuilding, if you encounter .0047mfd coupling caps be sure replace them with .047mfd.