Well since you ask, lets start with the Rega stuff.
First impressions weren't great I have to admit. Both the Apollo and Brio are pretty cheap looking in terms of their finish, and the volume and source knobs on the Brio feel cheap too. The actual underlying build quality is much better than it looks. I know aesthetics and tactile qualities come second to sound, but they do help to add to the overall level of satisfaction.
Sound wise the Rega pairing was very impressive in many ways. On simple, acoustic material the sound was very natural and airy and there was a good sense of the equipment itself being invisible. If all my listening consisted of stuff like Joni Mitchell and small scale jazz pieces I wouldn't have hesitated to put my money down. However, with more complex, larger scale material I had serious doubts. I found the sound a bit overly bright at times, which especially concerned me because my Wharfedales aren't exactly known for their brightness. The amp seemed to lose its grip when asked to play a full rock band or symphony orchestra in full flight and I could imagine it becoming tiring to listen to over a lengthy listening session. The Regas were also incredibly revealing of recording quality to the point where some things were harder to listen to than I want them to be. With the Rega R3 speakers in place of the Wharfedales, the many positive attributes of the Apollo/Brio combination came to the fore and the synergy was clearly stronger, but I still felt that the steeliness in more complex passages was too overbearing and it didn't convince me enough to part with my cash.
Listening to the Arcam A18 and CD17 again made me question why I liked them so much on first hearing. After the Rega kit, the Arcam sounded small scale and colourless and, although I could imagine it being a more amiable companion over a long session I could also imagine it making the music like wallpaper in the background. Don't get me wrong, in terms of soundstaging and timbre the Arcams are excellent, but they just aren't as interesting to listen to as I remember them and certainly not what I have been looking for.
The Denons combine some of the warmth of the Arcam with the excitement and sheer musicality of the Rega whilst avoiding the major pitfalls of either. The finish and tactile feel of the units is far better than the Regas and certainly as good as the Arcam FMJs. The feature set is also more user friendly than the Rega, including a decent headphone output on both amp and CD player.
If this were a group test I would award the Denon DCD1500/PMA1500 first place, followed by the Rega Apollo/Brio, then my previous Cambridge Audio 740A/C combo, and then the Arcam A18/CD17 in fourth.
At the price point below I wasn't very impressed with the Marantz PM6002/CD6002 combination (see my comments elsewhere for further detail) and would place it well below the NAD C325BEE/C525BEE combination which offers a much better balanced and more exciting and musical sound for similar money.
With regard to the various speakers I've heard during my search, I have continued to be impressed by the Diamond 9.1s on the end of each system I've tried, and I was also very impressed by the Rega R5s and Tannoy Mercury F1 Custom. I was, as I've already said, bitterly disappointed with the B&W 685s and cannot understand what all the fuss is about. Nothing I've heard has made me restless about my speakers and I feel that with my Diamond 9.1s, Diamond 8.3s and Tannoy Sensys 1s I have a collection of speakers which provides me with 3 very different but very high quality options to play around with according to my mood.