Yeah, 8GB is a drag. Apparently, memory on WP is not hot swappable. I've seem some hacks on other htc WPs that show that, deep inside of all these locked memory phones, is a normal microSD card (can't verify that for the Radar.) Even if you dig out this card and put in a higher capacity one, you'll have to do a hard reset to take advantage of the extra space. When the warranty drops out on my Radar I may just consider that. I'm a music lover too. I broke down yesterday and got a Zune pass. I love it. Nothing like hearing a song in a tv commercial, using Bing search to id the song and then instantly moving to marketplace to buy it and hear it (or download it) with the pass. Having a cheap data plan on t-mo with no fear of overage fees makes it even better.
I know Amazon lets you store your own music in the cloud (where you can stream it from them) for a low rate. Not sure if there is a dedicated interface app for that though.
The cloud is the future guys.
(by the by, love the IG references cckg!)