Just a note-
If the 2 cabs put out too much tonal difference getting a good mix is difficult. So, as cool as as you may think it is to have a 'woofer/tweeter' combination, if the soundfields are not balanced from the listening position you won't be happy.
I'd say go for 2 cabs that both sound good on their own, with no radical eq, just a bit different but complementary.
Not really a woofer tweeter thing as i have no intention of biamping. Just sort of in love with two sounds. Very good point, though. I'm probably still going to give it a shot just to satisfy my curiosity. I got the 4x10 for next to nothin'. If it sucks they come out one at a time.
What would you suggest as a good middle of the road 10" speaker.
I've done it several times, both in cabinets I made as well as in cabinets I purchased. I think the best one I had was one Vox Blue (8 ohms) and two Weber P10Q's (16 ohms apiece). Funny thing was, that combo made my Kendrick Bassman clone (w/KT-66's) sound just like my Blackface Super Reverb! I thought it was just me, but I had several people test the amps side by side... same conclusion. Weird, but true.
Which boogie cab is it? If it is the 3/4 back 4x10 with 18 watt Alinco Jensen speakers, don't even consider new speakers, as they are FANTASTIC. Bright but not icepick bright. I have one and it's the best cab I've ever owned. I sometimes run a second amp (G&K 250ML) with a Vox 2x12 cab, and that sounds pretty sweet.