Are Nakamichi amps any good?

I currently have a Krell KST 100 amp with a YBA 2 preamp driving my Vandersteen 2's but Threshold amps have caught my attention.

1) Would a Threshold amp be a step up from the Krell?

2) Are Nakamichi amps any good or are they Threshold wannabes?

I'm trying to keep the upgrade below $1000 and I'll recap amp if needed.
Although both were designed by Nelson Pass, the Nakamichi amps are anything but Threshold wannabes. I can't say how much of an upgrade you can expect over the Krell (which is a very nice amp). You may be better off updating the Krell. If you buy a Nakamichi, you won't be disappointed! I was happy with my PA-7.
Nakamichi was very popular in the late 80's and early 90's.
They do make a good product, just not as popular any more.
I have one of the Nak stasis units and it is very nice despite being an older design now. Get one at a decent price and you can't go too wrong and should be able to resell for what you paid if you don't like it.
I would take an amp designed by Pass over a Krell. The Vandersteen's are very detailed speakers and your old Krell, while well made and very powerful, may not be the best match. I think you would be very happy with the upgrade.
The Nakamichi amps had a reputation in the service industry for being unstable and prone to failure. They were not popular on this account even back when they were being made. They sound OK, but they are not the sort of amp that you want to push hard or abuse.
Nakamichi amps NEVER had a "reputation" for being unstable. They were a Nelson Pass design and well-respected when introduced, and still popular today.
They made a PA-7 and a PA-7 MK-2. The MK-2 is a better amp but hard to come buy. If you can find one at a good price get It. they are hard to find in mint shape tho.
I had remembered minor problems with these units from my years in the business, went to my old Tech, he said that the Nak amps had protection circuits that were a bit touchy and all in the original PA 5/7 really need to be replaced, but the series II didn't have that problem... Also on the Original PA series, there were minor issues with bridge rectifiers. He said that they certainly had to deal with those problems, but overall a sweet design and very stable amp.
Well, that's 2 techs who say the Nakamichi amps had reliability problems. Whether that's touchy protection circuits or bad bridge rectifiers, minor or otherwise.

I think it's safe to say that TonyKay is wrong and that Nakamichi amplifiers (regardless of how splendid a designer Nelson Pass might be) had issues.
When you spend a lot of time reading this forum, and others on the internet, you hear about individual issues with every manufacturer. Does that mean that every component is flawed and should be avoided? Of course not. It's one thing to say that a design had issues, but to say that Nakamichi amplifiers "had a reputation for being unstable and prone to failure" is simply NOT true!
As I understand it, Nakamichi bought the licensing rights to the Stasis technology from Threshold, Nakimichi presented their version of Stasis amps to Nelson Pass, who briefly tweaked it, and then Nakamichi went on to manufacture it with Japanese parts and construction.
The pure Japanese Nakamichi 420 is a superb sounding little amp.Only 50 watts but high current.
Better sounding than the PA7E in my experience.
Nakamichi amplifiers don't need defending. They were highly praised when they were introduced and still well-respected today. Ask someone who really owns one. If you can find one that hasn't been abused, and is selling in your price range, grab it it with both hands. You won't be disappointed.
Just in case.....I have several of the PA-7 and a few PA-7ii amps. Also a PA-5. These will be available soon. The "Stasis tech", was indeed, "used for a time", "Under license", from Nelson Pass. Until he left Nakamichi.
  He left, "Threshold", "Quite disgruntled" I hear. Over some disputes with his partners to go to Nak.. He did go back to Threshold for a time. Leaving finally to form, "Pass Laboratories", and then also, "First Watt". He also designed amplifiers for "Denon" back in the day! And probably for other companies as well.

These amps did NOT have horrible design issues by any stretch of the imagination! As far as any issues that I had with them?
 A nice corollary would be;

{My Ferrari must have design issues because two people stated here, that, "their", "Ford Station-wagon's"? Did not need as many tune up's as the Ford Wagon's did.....}

Fine Audiophile grade Amplifiers like these actually were? NEED servicing now and again. Just as my, "Pass Labs", "Krell", and also my "Manley Lab's", amps do in order to stay healthy and perform at the high levels they were designed to achieve. These were not, "Throw away", amps like many Crown, Pioneer and others were. "Once issues were found in that gear".
 And like a Ferrari, the Nak amps have also held their value "As Well As", Their sound!
 Whereas that old Ford wagon I owned? Who care's? But, It is In the junk yard, I am sure....
And , "Oh Yeah", The PA-7, Mkii amps are NOT a better amp than the PA-7. And do not sound as nice.
 Also, "Mr. Pass", "Invented" , "Stasis" tech. And- He did not, "Re-license", to Nak after he left. And that is when Nak built the PA-7, Mkii.
. This at about the time of Nak's, "Fall from Grace". Which began in earnest after Mr. Pass left, The orig. owner died and "Marketing", took over. "Onkyo" took the Japanese thrown for a bit and now?
 Sound united! Yipee!
 "Yes", It IS just that