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

The Audio Line out may not run through the processor? It may be for second zone stereo only. It may also be optional on some receivers to be full range stereo or L-R out of the pre amp processor. Some may even have this feature programmable by the source you have selected. I know this is not an exact answer, but there are so many receivers out there it probably depends on which model.

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.