I have a W5 and a W8 and have a Supratek. I have heard the W3 and its got the same signature as its big brother, the W5. Get a Supratek and you will be done! The 3000+ thread is not hype, this preamp is amazing!
I've tried three different tube preamps with my W-3 over the last few years. The BAT VK-3i was great, providing lots of tubey goodness, texture, and a huge soundstate. My current Sonic Frontiers SFL-2 is even better detail wise, with a bit less of that 'tubey' sound. My biggest disappointment was an Audible Illusions Modulus 3A; my unit was a nearly new example, but the gain was so high it sounded bright and grainy with the W-3, and had virtually no usuable volume adjustment range. The M3A also burned through pretty much every tube I fed it in short order.