Spend more money on the amp or the pre-amp?

Thank you for your thoughts thehorn!  Much appreciated. 

Though I cannot afford the jump from the NAD ($120, Craigslist) to a $1000 integrated tube amp. Though I will certainly keep those options in mind. :)

I'm more interested in the best possible "mid-fi" I suppose. 

I love the KEFs and they seem to be suited to my room (10'x15'). But I have the bass turned halfway down on the NAD and they still sound a little muddy sometimes. 

Another thought I had was to use the NAD as the amp and get the best sounding $200 preamp I could find. 

OK lemaze .... here's another suggestion.
Use the volume control on your Rega & run it straight through an amp.
For $200-$300 dollars you can pick up a used Carver M400, or a David Hafler DH-200.
An audio steel @ twice the price & both will put the NAD to shame.
I still have an M400 on the shelf, even though I've been using a Classe' DR9 for 10-12 years.
I've kept it as a back up for when I ship the DR9 back to Classe' Audio to get recaped.

Agree with those who say "integrated" and add a further wrinkle:

The more efficient and sensitive your speakers are, the better a cheap amp is going to sound.  People with K-horns report great results from TPA3116 chip amp boards (which have volume controls); I've paired one with some 91db/1watt Dahlquist DQM 9s and while the sound could obviously be improved on, the results are super suggestive of what could be achieved in this manner.

You stereo is a system; build it like one.

 

I would speak to your local dealer and visit him. He will treat you with respect and even more respect your budget whatever that may be. Build your systems with respect. Happy listening my friend.

preamps are obsolete, just use digital volume control ;)