ever used KT88 for bass and el34 for mids/treble

I run two Prima Luna prolouge 4 amps as momo blocks in my set up. I built my own cross overs for each driver, so I can bi or even tri amp my speakers. I use channel one for bass and channel two for mids and trebble on each prolouge four. My question is what do you think would happen if I used KT88's for the bass and el34's for the mids and trebble. Maybe best of both worlds? Any ideas? The primaLuna amps have auto basis, so I can use any combo of tubes I want.
"I use channel one for bass and channel two for mids and trebble on each prolouge four.

That's not a mono block setup, its a vertical biamp. Are you planning to put el34's in one of the channels and KT88's in the other? Or put el34's in both channels of one amp and the 88's in the other, and switch over to a horizontal biamp?
If you are really running separate amps not channels for the treble and mids on one and using another amp for the bass, then you can use different tubes. I think it should sound good or great. BTW how did you set up your crossovers?
I would interpret the question as referring to continuing to use the two amps in a vertical biamp configuration, but using EL34's in the channel of each amp which drives the mids/highs, and KT88's in the channel of each amp which drives the lows.

If so, a concern I would have is that the gains of the two channels would differ to a significant degree, resulting in a tonal imbalance. Unless, that is, the crossover network can somehow be adjusted to compensate. Or if you're lucky enough that using the 4 ohm tap on one channel and the 8 ohm tap on the other channel would happen to compensate sufficiently closely.

-- Al
Well I did buy 4 KT88 and installed two of them on the left chanel of each amp. I use one amp for the left speaker and one for the right. Then I use the left channel of each amp for the bass/highs and the right channel of each amp has the EL34's and they drive the Mids. The result is good. I think the speakers have a little better bass kick to them. I built the crossovers myself. The woofers are 18" with an SPL of 97db with 1watt. The mid horn is a Selinium 405 Ti driver with a big JBL lense and the high's are Crites horn tweeters. The mids and tweeters are rated @ 109db@1watt. So to balance out the drivers I have added volume controlls to the mid and Tweeter crossovers. My cross over points are 800hz/8000hz. I don't think using the kt88 made a huge difference in the bass, maybe it's more like a tweek. When I was building the cross overs, I swaped out Janzen caps for Audyn caps,  that was a night and day difference. The Audyn caps were much more open and life like sounding, a real improvement in the music.I think the type of tube your use is a matter of taste, a small pinch of taste. Speakers and source points will make the largest difference in a system.
Hi  yani55404

Can your amps handle the Tung Sol KT150 tube? The reason I ask is a friend of mine who is more a of tube aficionado than myself believes the Tung Sol KT150 tube in the right amp gives you wonderful bass and the mid range sweetness of the EL34. I like the Tung Sol KT150 tubes in my amp over KT88 or KT120 tubes.

Good luck.