Integrated for bi-amping with AtmaSphere MA1s


My speakers (Ascendo ZF3s) have separate terminales for each driver.  I am currently using Atmasphere MA1s for the mids and tweets, and using a Pass X1 and Aleph3 for the woofers.  I'm also using a set of old Entec LF20 subwoofers crossed over with a Behringer Ultracurve pro for the really low frequencies.  I would like to replace the X1 and Aleph3 with a more powerful integrated, and am not sure what to use.  I've been away from this hobby for a number of years, but my first instinct when I think low frequencies is Krell.  The S300i looks intriguing, but I've read that it comes from a dark time in Krell's history, and may not be terribly reliable, and not up to the stnadards of low-frequency reproduction Krell is known for. 
Is this a good choice?  What else should I consider?
honest1
@honest1



Review from 6 Moons on the Ascendo ZF3s :
"Finally in my opinion these speakers require really powerful amps to drive. It’s not obvious when you check their technical specifications as both sensitivity and impedance seem reasonable but my time with them proved otherwise."


This is the most likely reason to get a good bass mid/bass amp like I mentioned in my 1st post.
Spec’d at 5ohm "nominal" (the ZF3’s could be even lower in spots especially in the bass) and no mention of what degree of -phase angle there is, which could exacerbate any low impedance problems even further.

Cheers George
A lot of the amps, mentioned sound great, for bass.  I bet OP is looking to cool the joint off a bit, and still have plenty left in the tank... Not to mention, NOT break the bank.. I duno, maybe I'm just too studious..
I've heard the MA-1 a few times... I like SS bass.  I like the control, speed, and power.  More than anything, I like the loss of HEATERS in the summer.

The MA-1 is a cooker, but sure sounds good.  I liked them with small planars and line source cabinets.  That's my experience with them.

Regards
Thanks for the comments all.  I had been using the MA1s full range, with autoformers, but there was still some edge to the sound and softness to the bass.  Changing to bi-amping improved the bass and took the edge off the midrange.  I suppose all the fussing I'm going through to get them to work together is a sign the Ascendos are not the best match with the Atmaspheres, but they do provide the best sound I've ever had, and, in some ways,  some of the best sound I've ever heard anywhere.  But, of course, I'm always looking to improve.Heat can be an issue.  Most summers, there is a brief time I don't use the system much, but this summer seems worse than most.  I am thinking it might be a good idea to use the Aleph 3 during the hottest months to drive the whole speaker full range.
@honest1 have you tried tube rolling the 6SN7s in the MA-1? I was able to get the near perfect sound signature that I wanted by mixing different tubes, two of which Shuguang black treasures, those two especially emphasized the bass and took away any harshness from the highs. 
Yes, I m now running Sylvanias in the 3 middle positions, GE on the drivers, and RCA on the CCS.  The Sylvanias are good across the spectrum, the RCAs tone down the highs a bit.  I have not tried the Black Treasures, but I did get some rare Blue Glass Treasures (these were prototypes)when the Treasures first came out. 
This reminds me, I haven't been tube shopping in a while.  I should probably buy more NOS tubes before they completely disappear.