Don't know about that rega but I know that all rega stuff is well sought after. But on the pmc v spendor thing, I heard the spendors at Bristol and thought they were a big sound for the size. They were being driven loud and it was clear they were a small speaker though. The sound is a good detailed and all encompassing good sound with decent bass. But the pmc 25-23 which I own are more subtle, detailed and the bass is just more accurate. You'd expect me to say this but the pmc's are in a different price bracket to the spendors. But the a4 is competing with the old 20-23 speaker/price really, and it would have to be compared with that pmc, not the newer 25-23 model which just outclasses the old 20-23(which I owned too). Another thing is my amps are quite a bit better than the rega amps I think they were using at Bristol with the a4. But the pmc 25-23s transmission line, really low distortion, and improvements in mids and bass over the 20-23 make it a different proposition to the speakers in the 20-23s £2k ish price and I'd expect the spendor a4 too.
So my recommendation would be to think which amp you are going to use in deciding between the spendor and pmc, room size, as pmc's can really have loads more in amps. bear in mind too the pmc's are in a different class on the sound they produce to the spendor in working out which amp suits. Also the transmission line of the pmc's produces a lot more bass for the size of the speaker than the spendor can achieve with its arrangement, but totally different types of speaker obviously.