The Theater Master SL-9000 learning remote is supposed to have a very strong IR signal. I have a Marantz RC2000 mk1, myself. But considering how expensive it was ($250 new, $75-100 used) I can't recommend it over the SL9000, which seems to cost farless than the RC2000. But if you are looking for something with the features of the RC2000, but a higher WAF, check out the Marantz RC1200. It has a slim "cell-phone" like profile, witha jog wheel to control the screen.
The RC2000 is big, heavy (although I don't think so, myself), has a medicore IR signal, and crew thru batteries relatively quickly (2-3 weeks on 4 AAs). Of course I should play with the backlight sensitivity and timeout thresholds. Since obviously its the backlight that's chewing up the juice (i.e., it aint the IR strength folks!).