If you want to play with more than two pre-amp modules, you can get an RM4, M4, or M2 (or whatever its called). They are rack mounted pre-amps for using Randall and Egnater modules. *ONLY* the M4 and M2 can use both channels of the Egnater modules.
If you take that route, you will need some signal switching gear. The Voodoo Labs GCX (rackmount) or any 2+ loop foot switcher will work to switch between the RM50 and pre-amp. The Axxess GRX4 is pretty popular around here. If you want to get fancy-schmancy and blend pre-amps, then you'll need something like a Switchblade.
As long as they are wired and hooked up to your amp correctly you can never have too many speaker cabs. Your neighbors will disagree with me on this one.
Then there's your f/x. Almost too many choices here. The TC Electronics G-Major is great for parallel f/x (del, rev, chor). I don't like it for serial f/x because I think it sucks too much tone. You can also go the pedal route and get a different pedal for each effect. Or get something heavy duty like a Digitech GSP1101.
It's all in what you want out of your rig.
Thomas