Best Inexpensive Preamp for DENON 103?

I'm sure this has been asked before, but I am totally confused with all the choices and don't want to make another mistake.
My Cambridge 640P is actually not bad, but I know I'm missing on some dynamics, and the output is adequate but could be better.
Other components:
-Heavily modded Thorens TD-145 w/ a properly modded arm at about 24 grams.
- Rotel bi-amplification w/ B&W Matrix 802 vintage speakers.
- Budget right now, unfortunately, has to be capped at about $300.00

-1- I know I should pay more, (I can't)- anyone have something used they would like to move?
-2- I know there are better choices for arm and compliance- but take my word- this arm has been modded for weight, mass, and resonance control and is VERY acceptable as it is.
Just need help w/ recommendations!!

Which Denon 103?

I use 103R. It is a low output MC cart that has greater phono amplification requirements than many. I use a phono step-up transformer device with it and my ARC pre-amp to enable proper volume with low noise. If you have turn the volume knob up well past 12 o clock to get higher volumes, then this might be a problem. Check your phono pre-amps input sensitivity spec versus cart output spec to see if there is a discrepancy.
I previously used a Jasmine with various 103 variants and it was a nice phono and the de facto recommendation for Denons, but a hundred or so out of your range...

Lately I replaced the Jasmine with an older Monolithic PS-1 phono pre and am happier with its core sound, being more organic and natural with similar transparency and staging qualities. Dynamics may be a bit muted by comparison, but I have an HC-1B psu on the way which I suspect will give the Monolitich the advantage. Give it a look in your budget, I enjoy mine.

My other recommendation would be the Vista Audio phono pre AC addition for $300.
A Musical Surroundings Phononema might be had for $300 or so. I can suggest it because I did have a 130r with the Phonomena Nova (very similar but the Nova version runs off batteries) and the combo worked well. Both Phonomena versions have many DIP switches to configure the preamp for many different cartridges including LOMC.
A great sounding low-cost preamp that mates well with the DL-103 is a Jolida JD9. They come up used in the $300-350 range. List is $499. There are lots of well documented tweaks to improve performance to a much higher level.

06-12-12: Mingles
A great sounding low-cost preamp that mates well with the DL-103 is a Jolida JD9. They come up used in the $300-350 range. List is $499. There are lots of well documented tweaks to improve performance to a much higher level.

I was just going to suggest that. In fact, I upgraded from a 640P to a JD9 about 1-1/2 yrs ago and couldn't be happier. The gain and sensitivity levels plus the wide range of capacitance (for MM) and resistance (for MC) enable you to dial in a near optimum load and gain setting for just about any cartridge. It also has a "grown up" power supply and tubed buffer stage. I think it will wring a lot more performance out of your 103 without having to get into stupid money. Mine always strikes me as musical, organic-sounding, nicely transparent, exteneded at the frequency extremes, and never harsh or edgy.
This is my older post, but I thought I would update cause a couple things have gone down.

First, I purchased a used older edition Lehmann Black Cube on this forum for $240. Stock power supply. Huge improvement, as it should be, over the Cambridge. Better dynamics, HUGE soundstage (in comparison), less "congestion" on complex passages, etc. But after almost three months now, still felt something was missing especially with my SoundSmith- modded Denon 103. Still a bit of congestion, occasionally felt as if the low end was lacking on more and more recordings. I constructed a "D" cell dual-rail power source, and it now runs dead quiet. That improved overall dynamics and detail. But- it OCCASIONALLY sounds a little lacking in "air" in the high end, and I still feel it a bit lacking in the bass dept.

Next up, after more research and limited budget: The Jasmine (the latest) MKII, I think they call the newer one. Ordered direct from China about a week ago. I was tweaked by the very good reviews both here and elsewhere, and I was hearing the things I feel I needed in descriptions- Great dynamics, high output to help out my Denon MC, smooth, huge soundstage, "best value under $1000" (but how many preamps carry THAT title?)

I'm excited to get it up and running, but will temper my expectations until plenty of break in time.

Thanks all for the suggestions!