Best way to upgrade from Krell 400xi

I just bought a new pair of SP Tech 3.0 speakers, and I am thrilled to pieces with them. So thrilled that I am now dreaming of upgrading from my Krell 400xi. Don't get me wrong. The system sounds wonderful--I also have Musical Fidelity A5 CD player--but I'm convinced it could all sound wonderfuller, particularly with speakers this good. If I were to venture into separates, would it be better to buy a new amp and use the Krell as a pre-amp until making the next leap, or do it the other way around? Or simply buy a better integrated? I would appreciate your suggestions.
A friend just upgraded from the Krell 400xi to the new Pass Labs integrated INT150 - I'll ask him to post his impressions here.
Restock - it is a bit difficoult to compare the Krell to Pass intaegrated, since the both offer very different perspectives - 400xi is a typical flavour 1 sound(fast and transparent), and Int150 is a flavor 2 (a bit warm and forgiving).

If you want something similar to Krell in overall charakter, only better, look for sth like Gryphon Callisto 2100/2200/Diablo integrateds.
Elberoth2, IMO the 400xi is already on the slightly warmer side for a Krell. The new Pass integrated is faster, more detailed and more transparent than the Krell. It is slightly warmer and not quite as dry as Krell. Tonally the difference is not that big, in terms of resolution, instrument separation and sound staging it is.

Maybe I can offer my perspective on the comparison of the two units, since I just upgraded from Krell 400xi to Pass Labs INT-150.

Th Pass INT-150 is Nelson Pass' first foray into designing an integrated amp. It is essentially a X-150.5 stereo amp and a simplified version of the new XP-10 preamp. It runs in class A for the first 10 watts before switching over to class AB.

My initial impression? Well I am smitten by the sound. Let's get the negative out of the way. This is not the greenest of amp, it draws 225 watts of power in idle and 600 watts at peak. Although this amp is supposed to run 20% more efficient than previous design, it still runs pretty hot but not too hot to touch. This is all the negative I could find so far.

Compared to the Krell which puts out 200 watts per channel, this Pass is rated at only 150 watts. However, in actual operation, the Pass sounded like a much more meaty amp than the Krell. One magazine review rated the X-150.5 as having a 250 watts output at 8 ohms, so the amp is likely seriously underrated. It absolutely kills the Krell in explosive dynamics, high resolution and ease of flow and the Krell was no slouch in this department.

The amp has a lot of the legendary sound signature of all Pass products, like the Pass Xono phono preamp which I also own. It is warm, lush and sweet, with a deep soundstage and yet has details and tight bottom end to die for.

One of the nice things about having pure Class A for the first 10 watts is that you can listen to the system at low level and still get that gorgeous sense of musical flow and low-level continuity. When you crank it up, the amp really puts my Dynaudio Special 25's through their paces. The amp renders all instruments with an astonishing accuracy of timbre, liquidity and ease of flow. Dare I say almost tube like, but not many tube amps can produce the kind of dynamics the Pass amp can put out.
Try an Onkyo A 9555 integrated. Build quality is nearly identical and it should sound much better. Check the reviews.
Onkyo A 9555 better than a Krell 400xi? PLEASE...
What are you smoking?
I don't smoke anything but a lot of things smoke Krell.

Once you get past professional reviewer claptrap and historical presumption, there really isn't all that much to be had from Krell. However, as long as you continue to convince yourself otherwise, there will be no room for argument or discovery and you will stay happy.

So, for the record, I don't agree and that doesn't matter.
Your dealer loves you.
Admitedly my knowledge of Krell is rather limited, but if I was shopping for a new (intergrated) amp the Symphonic Line amps would be on my short list.