First question, why do you want to upgrade? Is it:
- there's something you don't like, e.g. you'd like to move away from the Naim presentation style?
- you've got some dosh and want something better
From experience, I'd suggest you look at your speakers next.
The key reason I say that is that synergy between amp and speakers is far more important than whether each individual element is an award winning unit. In general speakers are the most personal choice for a person, mainly because there's a bigger variance in how they present the music, additionally, you need to ensure that you can get them to work in your own room.
So my suggestion is that you find the speakers you like, then get an amp that will work with them.
The standard route is for people to have come in from getting used to the usual 2 way ported standmount. At the kind of price point you should be looking at, there's actually a shed load more choices, e.g. electrostatics, horns, infinite baffle.
