I bought the Zen Xtra 30GB last week, I love it. The actual unit, the software, and firmware are all improved upon over the Zen NX (which I owned for one month before selling on eBay). Of course, its price tag wasn't cheap.
got well over 20,000 tracks here on just my main media HDD (Music folder is nearly hitting 100 gig) - it's not all my personal collection.. me + my bro. Even know a cousin who has more than that.. but he's simply a music phreak
As for my mp3 player... well it actually main form of portable audio player is my phone - it plays ogg files (half the size of mp3's) ... with 128 MB memory stick in there... have around 40-50 tracks on there... takes roughly 60-70 MB - and those tracks normally last me a week before I update them.. sometimes even longer.
I didn't know people like you even existed. I only keep my favourite tracks in my personal collection and throw out the rest. There are only so many tracks you can listen to in one go. CD player still beats memory stick in terms of economy. Up to 850MB music compared to 128MB memory stick.