Nitron shocks are good and the main reason for that is allmost every internal part is a direct copy of the Ohlins internals, Shim stacks/pistons,amount of oil, air PSI and even the computer software used to check everything is working correctly is taken from them. The only real diffrence is the quality of the components but there isnt alot in it. Ohlins are just making a bigger profit, Ktech sell some real high quality stuff and if i had the money thats where it would go, maxton sell some good stuff but it isnt quite up to the standard of Nitron.

Things may have changed a bit now but thats how it was a year ago when i worked for Nitron. Ohlins and Ktech are definatly better kit thats why Scott(the lad who makes the bike shocks there) fitted Ohlins to his blade its worth the extra money if you want that extra bit of performance IMO.

I can't pass judgement on others other than Ohlins, which I have fitted to 4 of my bikes and the engineering quality is good. The Penske seems nicely made too, but as I haven't used it yet it's hard to say.
As a guide I paid £300 for my used Ohlins for the NC30, it had a receipt with it for a service, with a reputable company. For that kind of money I'd have been looking at a Hagon or cheap Nitron model