Not a pro and not (really) a felder, but I do have the 79" Hammer B3. I can try to answer any Q's you might have on it from my experience but consider that I'm not a pro and have relatively low usage.
I'm going to echo what a lot of the fog (felder owners group -
http://finance.groups.yahoo.com/group/felder-woodworking/ you have to ask to join, but they let me on so..
) would say and shop around for used if you're looking for the whole enchilada. I wouldn't limit myself to a felder in that case as I see altendorfs and MM's (and occasionally Martins - hey a guy can dream can't he) go for reasonable dollars (in some bizarre sense of reasonable .. compared to new anyway) somewhat regularly.
For instance
http://dallas.craigslist.org/ftw/tls/3376477662.html "Altendorf F45 Sliding Table Saw - $13250 (Downtown Ft. Worth)" - sweet!
http://hickory.craigslist.org/tls/3390296818.html "Felder Commercial Table Saw - KF700S - Single Phase 220 Volt with digital built-in router." $6500
Also check
http://woodweb.com under Buy/Sell->Machinery Exchange->Panel Saws-Sliding
and
http://www.exfactory.com/
or felders used market
http://www.number-1-mm.com/us/en_US/format-sliding-table-saws-9.html (has a nice K975 Professional at the moment, no idea on price).
If you do find a used Felder, I'd personally try for a post 2006 X-Roll (because well the people who know more than me say its better than the previous generation
).
I would argue that a well cared for Altendorf or Martin would be close to par or better with a new Felder, their Format line is even nicer. Once you consider that you're pushing 10K for the 500 series and somewhere over that for the 700...