Help My Krell amp is too big.

How about the new Ayre MX-R monoblocks--only 18 3/4 inches long. From the Ayre website:
Dimensions
11" W x 18.75" D x 3.75" H
(28cm x 48cm x 9.5cm)

But probably too beautiful to hide in a cabinet! There is a new review in Stereophile.

You must have forgotten the proper sequence to getting things done - You build your new home to fit your audio system and not the other way around :-).

I would suggest you not sell off your Krell but instead try to work with what you have. Firstly they are good amps and secondly it is not advisable to place your power amp in an enclosure. You'll going to have heating problem, regardless of whatever amps you are going to get. The only amp I know that does not get too hot are the McIntosh because they are class B amps. If you insist on fitting your amps in your cabinet and the McIntosh sound fits your taste, you might want to give it a shot.

Bust out the back of your stereo cabinet. Have a carpenter bust it out and expand it into the stud wall, there's atleast 4" hidden back there. I've seen it done for TV's, why not your amp?

Will the stereo cabinet allow for adequate ventilation of your Krell?

If you like Krell sound why not stay with Krell mono?