If you're going to use an external source (a drum module) to trigger Ultrabeat, you need to map the drum module's MIDI Note outputs to Ultrabeat's standard mapping. Ultrabeat (in Logic 8) uses C1-B2 for its mappings. Check you manuals for Logic 7. For example, the Bass Drum in most ultrabeat out-of-the-box kits is set to C1 (the standard GM note).
There's two ways to do this. You would either have to change the output from your drum module for the Bass Drum trigger to C1 or change the patch in Ultrabeat to whatever note your Bass trigger is sending. A quick way to check the mappings from your drum module is record it and see in the piano roll what notes are sent. I hate to say it, but with this kind of thing, it's time to dig into the manuals.
Regarding choice of Drum module, as long as you can set the MIDI Note outputs in the module, it doesn't matter much. I used to own a DM5, but hated it mostly for the internal sounds and that it can't handle dual zone triggers without Y-cables. I never tried linking to any computer based DAW. I have no experience at all with the Simmons. Unless you need internal sounds from your drum module, I would check out the Alesis Trigger I/O. For less $$$ than a new DM5, it supports dual zone pads, has a built in USB interface and comes with a teaser version of BFD.
One last thing, I use a Yamaha DTXPress II to trigger DFHs in LE8, and DFHs has a learn function which makes mapping really easy. The sounds I get out of it are unbelievable.
