I did this for a little over a year in a covers band, certainly has it's advantages and disadvantages.
Regarding amplifying it, we always just ran it through FOH, what are you using for a PA? I don't think playing it through a bass amp is a good idea, both from a volume and tone perspective. Nothing will weaken your performance more than the instruments overpowering your track. We used a HK system with 12" and horn tops and 18" subs. You don't need something quite that big, but I'd be concerned about doing it without subs of any kind.
I also think that you'd be better served learning how to program in midi drums, rather than using a session drummer. This nothing against session drummers, that would be the best way to get a good sound with a good live feel, especially if none of you are experienced at writing percussion, but my concern with regards to originals music is that it could be very limiting. It's a big commitment to the song basically never changing ever again, unless you want to pay to have it re-recorded. Maybe there's only little hit out of place, or a fill that doesnt sit quite right, and you don't notice at the time, until one day you can never stop noticing it. Plus this way, you can add any other VST intrument you can think of. I guess it depends whether this is a stop-gap until you get a drummer (in which case get a session recording), or how you plan to be doing this ongoing (in which case, to me, it's not even a question, VST all the way). That you're looking at buying gear for it suggests the latter.
I write the tracks in Guitar Pro 5 (6 can go to hell), I import the midi into Ableton Live, and I use Superior Drummer 2.0 as my drum VST and iZotope Ozone to master it. I've been using guitar pro since before I was playing bass, so maybe it's more of a learning curve than I realise, but to me it's the best solution. You could always just write midi straight into a DAW (digital audio workstation, Ableton is one of these), but I prefer writing tab, it's just a preference thing.
Here's a really crappy recording someone made with their phone of us playing a gig to tracks. The keyboard solo is also a good example of the other things you could incorporate using this method (I know it's a bit lame to have a solo with no one playing, that's not actually what I'm suggesting you do). We never really had any problems keeping together, and we didn't use a click; like, it's a drum track, it *is* the click. Guitarist had to have his fold pretty loud, but that's about it.
We don't play to tracks anymore, and I wouldn't go back to doing it, but that's only in a covers context. If I ever actually get enough market-friendly original music together to perform it, this is probably how I'll do it.
