First I'd like to thank you all for the comments on this thread.
Well I went to the music store the other day to order the combo but they said it's on backorder for about two months. And I did'nt want to wait or the money would surely burn a hole in my pocket.
So I bought a new M6 rackmount head that they had in the store and went straight to band practice that night and hooked it up to my Peavey 4x10 and 1x18 (both 8 ohms) and man, I've never felt these old clapped out speakers move like that before. The only head that has ever been on top of those speakers is the old Peavey Mark VI.
I set all the EQ controls flat (on the M6), the gain at noon and the volume at 8 o'clock just barely cracked open really.
This head has the sound that I thought me or my speakers could never produce.
smooth mids and highs, deep lows and warm and punchy, as you can tell I love this thing.

Can't wait till I can afford some new speaker cabs in a few months.
I think this amp will make me a better player too as I can already tell I need to refine my playing on some things.
Well I guess you could say I'm still in the honeymoon phase. But so far this thing is killer and everybody in the band loved it, especially my drummer who said he could never hear me with such clarity and definition before.
I don't even think I was as loud as I was with my Peavy head but it sure seemed like I was and I just like the punch and feel of this amp.
I surely was'nt disappointed.
While I'm still curious about how the combo would've sounded, it kind of worked out good for me because I can easily take the head with me when I leave band practice or gigs and I have other speakers to hook it up to at home, rather than moving the combo back and forth.