Best power source (value for money) for NAC 152xs?

With the NAC152XS the Flatcap is still rather useful as it can still be used for powering the logic and control circuits.  This brings big gains all round by separating these relatively noisy circuits from the audio supplies.

Thanks! So if I understand you correctly a NAP 200DR will then sound better than a non DR 200 together with my flatcap?

Probably.  

I haven't tried, so couldn't tell you for sure.

I wouldn't sweat over the NAP. Just get yourself a NAP155XS and a pair of Allaes. Then sex up your sources as far as you like  :-)

I used to run a Nac152xs with flatcap xs on both upgrades on the 152 and a Nap155xs.

It was an excellent well balanced system. The flatcap xs was a very nice upgrade on the standalone 152xs.

If you get the 200 (DR or not) you will likely get the matching 202 before long, making the 152 and flatcap redundant.  If you're on a budget just get the 155 and be done with it.  

And once you've got the 202, the 282 will start to look tempting...

I kind of feel stuck with my NAC 152 since I am also using an N-Sub which I don't want to be without and since the finer pre amps don't have a sub-input I don't want to upgrade :-) I can only connect the sub through rca-cable since I am using an antimode (DS Speaker).

You could take a pre-out from one of the three stereo outputs from the power supply.  You just need to ensure the sub lead is not overly capacitive and is appropriately slugged (IIRC Naim use a 100R resistor in they sub lead) to prevent instability.

Oh, thanks so then I would need a din to rca-cable to connect from my flatcap?

And will using one of these stereo outputs be as good as a dedicated sub input in my 152?

Yes, DIN4 - RCA.  Naim used to make a DIN4-2 RCA Sub lead just for this kind of scenario in 5 or 10m length. It had the resistor fitted in the DIN.