1)... but our guitar player likes to full blast it at all times typically.
If you get a bigger amp, the guitard will turn up more. Obviously he likes drowning you out and is not concerned with the overall sound of the group.
So the while the guitar is blasting, the drummer is pounding, lil ol' you is left to figure out what to do.
Your solution is to spend your hard earned cash on some rig that may or may not cut through the noise that your band members are producing.
Obviously, the guitard is the problem.
2) We have been talking to him about his issue and how it takes away from everything.
Time to stop talking. The guitard is not only ruining your rehearsals but also your hearing. Either he's going to be in the "band" and stop playing a semi-solo gig or not.
Here's what I would do:
Reduce the drummers volume:
1) get some sound board from your local hardware store. It usually comes in 4'x8' sheets. They can cut it in half at the store, usually. So you have 2 4x4 sheets. Set the drummer up in the corner of your rehearsal space. Hang some blankets or carpet on the walls behind the drummer. Next put up the sound board creating a box around the drummer. You can use some duct tape to create a "hinge" for the sound board so it won't fall over.
2) Raise the bass amp so it's at ear level. Set it up right next to the drummer so he hears you well and so you can lock in with him.
3) After you get 1 & 2 done, then you and the drummer do a sound check and get to a comfortable rehearsal volume.
4) Then do a sound check with the guitard, with him starting at a very low volume and start increasing until you and the drummer agree that his volume is okay. The guitard has no vote. If he "needs" to hear himself better at the volume you choose, raise his speaker box to ear level so he can stand right next to it. After he gets his tone adjusted and the volume is still satisfactory to you and the drummer, by agreement, he is not to turn up the volume.
Note: if he has a tube amp and want the saturated power tube distortion, he can get an attenuator (power soak)
http://cgi.ebay.com/THD-4-ohm-Hot-P...ryZ43375QQssPageNameZWDVWQQrdZ1QQcmdZViewItem to get his tone with volume still set just right for rehearsal. Or a tube emulator
http://cgi.ebay.com/VOLUME-BOX-Atte...ryZ10171QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
5) Do a full rehearsal like this and see how it goes. If the guitard goes back to his old ways, you and the drummer (by previous agreement) stop playing until he turns down. Either it's a "band" or not.
This is the age old story of LGS (lead guitar syndrome) overshadowing any sense of reasoning or logic.
Good luck.
btw, you should be wearing ear plugs, no matter if it's a rehearsal or a gig.
If you really want to go beyond a newbie, I suggest studying the following threads:
Best musical advice:
http://www.talkbass.com/forum/showthread.php?t=434246
If I only knew then what I know now....
http://www.talkbass.com/forum/showthread.php?t=429034
Hearing loss and ear plugs:
http://www.talkbass.com/forum/showthread.php?t=445683
Good luck! (and don't back down).