I've used a 103R since April and couldn't be more pleased. Reports on the quality of this cartridge are all over the place, although most of what your hear about the 103 and 103R is positive. Mixed reviews seem to abound, however, with the Rega arms with some users having good luck and others none at all. From all the reading I've done, it seems to me that the 250 is a poor match with the 103 and 103R while many users may be happy (or unhappy as it may be) with the 300.
For what it's worth, I use my 103R with a Premiere FT3, a fairly low budget medium mass arm. The FT3 does have damping capability though, and that damping capability makes a substantial difference in the performance of the Denon. A poster at the Vinyl Asylum recently pointed out to me that in reading that he had done it recommended that the Denon's be used in either a high mass arm or a medium mass arm with damping capability. So for those out there with medium mass plus damping, the Denons could be your ticket. I've also found that about 4.5 to 5 grams of blue tak on top of my headshell made a subtle but definitely audible improvement with the 103R. My FT3 is on an older Michell Gyrodec and I'm using a decidedly low budget phono stage (about $200 retail), but the 103R easily and grossly surpasses the Ortofon MC 20 Super I replaced, which was a) a much more expensive cartridge and b) supposedly a much better match in terms of compliance with my tonearm.
So experimentation may be in order for you. At $250 the 103R is a pretty cheap experiment that, as one poster above pointed out, you can probably recover most of your money on if it doesn't work out. And if it does work out, you will probably be very happy. When I bought my table used many years ago, it came with a Koetsu Black which I used for a number of years. I can buy 6 or 7 103R's for one Koetsu Black and, although my system may not have been as good (and it's still pretty middle of the road or even low budget compared to most Audiogoners) in those days, I can tell you that is what I intend to do. I feel absolutely no need to buy anything other than a 103R. In my modest system, it does a lot of things right.