First, I would double check your price point with ebay. Unless you are signing a new contract (or maybe an upgrade) with Cingular, ebay will normally be your cheapest price. That being said. I don't think you can get a 6682 for under $250. You might get lucky and get an auction for close or at that value, but don't go in expecting that to happen. The Cingular 2125 is even more expensive and is suffering from a shortage, so the price has gone up a bit.
Not to put a damper on the mood, but that's one of the things that kills entusiasm. You decide on a phone, and then its about $100 more than expected and you have to start the process over again, or just be patient (I hate being patient).
All that being said, there are a billion and a half phones that can play mp3. You will want a phone with an 850 band so that cuts it down to a smaller number, but if you can get by with using Cingular's 1900 band then you are back to the billion and a half. Look on www.gsmarena.com, and start browsing. Look under features, and if it has an MP3 player it should list it.
As far as the phones you are looking at right now, the HTC and windows mobile platform can do more streaming and video work natively. The real player on the 6682 (or all nokias) isn't that great, but the Symbian operating system allows you to replace the crappy installed programs with better built ones. Windows mobile is new, so you might run into software compatibility problems when trying to expand your software library. I personally hate the 6682 keyboard with a passion, and physically can't use it. The HTC doesn't look that much better, but if its closely related to the SMT 5600 then its a pretty solid keypad.
Otherwise, there is not that much between them. For simply taking calls and playing MP3s it might come down to which is the better deal. Looking at ebay, that would go to the 6682.
