Wishing you well, it's a landmine out there. Here's what I know:

AMD 'main chip's are better and cheaper than intel so don't let anyone bs you that you need an intel,you're paying a premium for nothing.

Tiger and Computer Discount Warehouses are dependable mail order outfits which sometimes run great closeout deals (may not be the hottest and latest, but that may be fine if you can get something functional for $300). If they have nothing you like, you can turn to Dell. Gateway's another way to go but they've hacked off a lot of folks lately.

Office Depots/Comp USAs etc sometimes have "refurbs", new units which were returned within 30 days. Often the main problem was user error or buyers regret, but they're not "new" anymore. Ask the salespeople if they've got any, sometimes there's one in the back being checked out, can be a nice current machine with hundreds of bucks knocked off the price. If you know of a local small computer shop, they may also have gently used units for a good price, it can't hurt to ask.

What do we use? At work, a "Howard", a nice heavy duty clone proudly made in Mississippi. At home, a screamer home-built by the resident guru. Home-built is definitely more expensive. But it's an addiction, so sometimes these guys have a nice machine they've abandoned for something faster, pays to ask your geek neighbor if he knows of one like this he could sell, hell sometimes if they're flush they'll pass them on freebie to get them out of the house before they're obsoleted in another year or two.