is an RCA "pre out" same as "audio line out"?

There are some Factory Refurbished receiver at accessories4less.com : Denon 3312, 4310(no 3d) and Marntz 6006 all within your price range. I suggest you download a owner manual like this one, and read how a modern receiver setup, page 21 is what you looking for.

Look for a used B&K receiver. A great bargain if you can do without HDMI. Made in the USA. Built tougher than most of the import gear.

No, the line out is different. It is at a fixed level that cannot be hooked up to a power amp. You need the preamp outputs. If it states "pre-out" look up the owners manual on the net to double check that one. Actually, before you hook any of the preamp, or "pre-out" outputs to an amp, double check the manual to make sure it's a variable output. I've seen a couple have a variable/fixed option in the past. A lot of companies put their manuals on the net now.

If you hook an amp to a line out, the volume could be loud enough to blow your speakers. The volume does not change with these outputs. These outputs are for tape recorders, processors, CD recorders, etc.

Outlaw Audio has their new Model 975 processor with all the latest bells and whistles for under $600, about what one would pay for an AVR with full set of preouts.

http://www.outlawaudio.com/products/975.html

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I believe you mean you are shopping for a 5.1 or 7.1 AVR (Audio Video Receiver). If so, Imhififan gave you a list of some good AVR's to consider that are being cleared out at or below your budget. Also, consider the NAD T748 being cleared out way below your budget through various reputable internet dealers. All of these models have a full set of PRE-OUTS. Finally check out Best Buy/Magnolias this time of year for great deals on demos & open box units. All have full warranties and return privleges and in most cases, absolutely nothing wrong. Good luck.