Nice find, the E46 rocks. I don't know about the convertible, but IMO, the coupe is even more fun and tactile than the E9x (at the sacrifice of total speed, grip, and comfort). The convertible will probably be a little heavier than your E92 coupe.
Expect to replace your RTAB's relatively soon (within 20-30k miles). Without fresh RTAB's, your car won't hold an alignment properly causing strange handling and fast tire wear.
M3 Sedan - AW/Black - 6MT - no moonroof - no folding seats - RAC RG63 - clear bra by Omega Werks