The 902 is a very nice driver, although as sootshe pointed out, you'll be missing out on the excellent high-end of the driver if using a tweeter. In my search to upgrade the k55, I ended up with the JBL 2470 (another phenolic driver, like the k55) and have found it to be a good match, smoother than the k55, nice body in the low end. If you're strictly looking for new, I'm sure others will speak up with recommendations.
Ah yes I aspire to JBL. After a full H/T music system from scratch that will have to waite till another day.