Operating Systems

[Mythril Gear]

As some of you already know, I am an Operating system freak. I've used every version of Windows from 3.0 (3.1, 95, 98, 98SE) to ME, and 2000. I've used several types of Unix too, including Linux (Slackware, Mandrake, and Storm), HP-UX, and Solaris. I've even seen some more rare OS's like BeOS. I also, on occasion, have used MacOS (some 6.something - the OLD B&W one, to 7.x, the newest MacOS, but I haven't seen OS X yet...)
During all my travels, the two OS's that stand out above them all are Windows NT 2000 and BeOS. no matter how many I try, none seem to match Windows for ease of setup, hardware and software support. Linux comes *kinda* close for software support, but BeOS is the king of hardware. (It's really quite an indescribable experience, you must see to believe... It's coded so well that it NEVER crashes badly enough to reset your system, and it's fast as all heck! If only it was still in development, it would be the perfect OS, alas.....)
My question to you is: I am bored, I wanna install another OS on my PC. I have over 40 gigs floating around. What should I go for? I was kinda thinking Linux, but that's old hat (a pun on Red Hat, get it?), however it is the most usefull of the non-windows OS's. Then I was thinking I'd do BeOS again, but it was completely useless as an OS to do work with, because of its pitifully small software base. If only MacOS X was out for PC...
So, I am looking for a hardware-hacking, hdd-stretching, multi-booting, cdrom-dumping, configfile-seraching, cpu-busting challenge. It has been such a long time since I had so much fun with my computer. What do you propose I try?