cabinet question

I have a Marshall 1960A 4x12 cab. with 4 G12-T75 speakers in it. I also just purchased a Peavey Triple XXX head. This thing sounds awsome. My question is......I was thinking about changeing the cab's setup like the new bogner uberschall cab with 2 vintage 30's and to T75's. My question is how would I connect the speakers up to the existing terminal so that plugged into one slot it's 16ohm, and plugged into the other slot it's 4ohm, and plugged into the 16ohm of two cabbinets 8ohms. How much would the sound differ and in what ways? I'm all about getting the best tone I can with the gear I've got. Any help or opinions would be greatly appreciated.

This doesn't really help that much with your technical question, but I figured I'd give you a comment or two about the Peavey Tri-XXX and its tone. I run a Peavey Triple XXX Head through a Bogner Cab loaded with Vintage 30's, and the other guitar player for my current band has the same Marshall cab you have. Through either cab the head sounds beastly, especially if you're going for that sort of "Swedish" Metal sound (In Flames, Arch Enemy, etc.) My band plays in the style of In Flames / Children of Bodom and for our demo we're recording all rhythm and lead tones were recorded with the Peavey head and the Marshall cab. The results were awesome. We have some very heavy sounding stuff and the quality was more than I ever expected. But I will admit that in a life setup, the head seems to sound a lot better through the 4x12 with Vintage 30's. The tone is much more thick and heavy sounding, as well as there being quite a bit of low end. Just some thoughts.

What sort of guitar are you running? Do you use any pedals? What style of music do you play?

I play an 01' PRS custom22. I don't have any effects pedals, but I do have a PODxt. I don't really use it in my live setup, but I have it running through the effects loop, incase I feel the urge for some reverb, delay, or chorus. I'm not using any amp settings on it, just have it switched to bypass all that. I play a wide variety of styles. Mainly modern sounding hard rock to metal, but I enjoy playing everything from bluesy stuff, to classic rock, to hardcore metal. Rhythm guitar is what I enjoy most, but occasionally I'll pull out some lead stuff. BTW, where do you usually have the damping switch set on? I find that having in in the middle works best for me. But, I haven't had the head but for 6 days now, so I've still got alot of minor tweaking to do before I have it set up just right. Does anybody know how this head would sound with EL34 power tubes instead of the 6L6 tubes?