Most keyboards that sport only mIDI In and Out let you use the MIDI Out socket as an optional MIDI Thru. Shouldn't be a problem. ...But in case you're going to add more MIDI synths in the future get yourself some simple 4-Port MIDI interface and save yourself the trouble of having to deal with MIDI Thru.

cheers

PS
B4 II and Lounge Lizard should be okay since they are CPu friendly. The UVI engine on the other hand (sample playback engine used by Spectrasonics and Ultimate Sound bank) can be a bit of a CPU hog. On older machines anyway. At least I couldn't really load more than one or two instances of UVI based soft synths on my old Mac G4 (933Mhz PowerPC). exporting audio off-line took just moments to do so it wasn't really an issue for me. My new dual 2.7Ghz G5 can handle virtually unlimited amount of soft synths (even the ones I once considered to be CPU hogs) but I still bounce to disk. I'm used to doing it that way I guess.

[This message has been edited by 3351 (edited 12-15-2007).]