^I just use a slide card on my newer fat PS2. Didn't feel like playing imports on a slim since it takes more work imo (and I'm used to using the slide card).
I got the DDS boxset new for 40$ I think, and with it I got the extra cd of the game music with it.
Then I got DDS2 new on Amazon.com for $20 bucks I think.
It's just harder to find these games since there weren't as many published as your typical games like say Final Fantasy or MGS (me thinks). So that's why they're usually more expensive when you do actually find them.
All in all DDS has been my favorite of the SMT games. Persona runs a close second, but in my own opinion at least, DDS is alot like Persona, just more. The only thing I didn't really like about DDS was the dungeon size, but the story was great and not that cliche.