Hi, I recently went amp-hunting on this budget... I have a much modded rega TT and was running an old Rotel 930BX amp through some MA BX2 speakers. I tried the A19 and found it to be a very competent amp on Richer Sounds test system... as well as the in-built MM I tried a CA 651P phono stage, which I was also running at home. It didn't give me the step-up in dynamics I was looking for... but this was probably down to the TT and (frankly) poor stylus that RS was using.
Tried a Cyrus 5 amp with the 651P, which was the 1st time I've heard Cyrus... very punchy, detailed and dynamic, but for me too much so... it lost the musicality and fluidity I like from my Vinyl.
Also I had demoed a Naim Nait 5i earlier in the day - a little over budget, but this is a really special amp I think.... I demoed first through the MA BX2's (bought mine from home) - nice - but then made the mistake of asking the dealer to match some 'speakers of choice'. After listening to a £1000 pair of Neats I was totally sold, but I didn't have £2k to spend on an original £800 budget! I think you really need to system match to get the best out of Naim and its an expensive and possibly limiting path.
So I then tried the Roksan Kandy K2, which I ended up buying. Great amp, great look, nice in-built MM - highly recommend and possible upgrade options through purchase of power amp. I must admit, I managed to get this and some matching Roksan speakers 2nd hand on my budget - big step up 🙂
From all of this, I realised 1st hand (had read about it lots) that personal taste, system matching and a whole host of other factors come into play - cool, but a little daunting at first. Hope my experience gives you some more ideas. As you have a Marantz CD, I would recommend maybe trying a Marantz amp? I think the KI Pearl Lite would be in your budget.
Cheers