With the hamfest season upon us, you never know what you will find...however, that being said, the 320 is an excellent way to get started, if you wish to explore the HF world using your PC. I would suggest joining the 320 Yahoo group to see what software is compatible with Win7, but there are several packages out there that are quite capable. The current version of the 320 now includes a USB port, but how that plays out with the current batch of software, I don't know.
I do know more than a few folks (including 1 or 2 MT editors) that use it as either a primary or backup receiver. It has up to 32 different bandwidths, and is more than capable of hearing DX (I have one, and did hear a good bit just with a loop in my attic - which I had to take down, darn it...). You can research reviews using the links found here...
Category:Receiver Reviews - The RadioReference Wiki
Check out the eHam General Coverage and NASWA links. In fact, for whatever rx you wish to investigate, keep that receiver reviews page handy. There's a ton of reference material there.
As to software support - there are several much older packages that may run in Win7 in compatibility mode (Clifton Turner's controller, Scan320 among them), but here's a few titles you might want to look at:
-Callsign ScopeStation
-DXtra
-Ergo
-RxPlus
-RxWings
-Shortwave Log
All of these are linked from here...
Receiver Software Applications - The RadioReference Wiki
And one more...
-TRX Manager
found linked from here...
Amateur Radio Transceiver Control - The RadioReference Wiki
Now as an alternative, I see someone has the Eladit FDM-77 on the Universal Radio used list for 349.95. Unfortunately there isn't nearly the software support, but it does give you a toehold into the world of Software Defined Radio.
Keep in mind you will need a good antenna (preferably outdoors) to make full use of rxs like these, so you avoid hearing your PC instead. Indoor antennas can be used, but it can be a bit of a challenge to make sure you don't run into this issue, particularly if you are in an apartment or condo. I'm in that boat now, unfortunately.
Lots to think about. 73 Mike