Hi, your room is not the smallest and your budget is just fine. Kef ls50 meta will be fitting to your room. Rega Brio is very very good amp. It has no problem to drive Kef ls50 meta. Just this speaker has very high resolution and accept no compromise in setup. You will need excellent source of signal, say some 1500 eur and more. Is not important if digital or analogue. And cables and stands of course. I do not know which CD Marantz you use. Brio is very universal and musical with full sound and also good fast bass in small to mid rooms. I have still Brio 2016 (last model) in my small system. I use them with czech Xavian Delizia small column speakers. Brio works well with Fyne Audio, Cabasse, Dynaudio (like small Emit range - real bargain), Dali, Totem Acoustics, Triangle is also excellent with Rega amps. Something like Dynaudio Emit 10+ stands will work well with Brio in your room. I have had also old Rega Jura speakers. As used, you may get them for 200 -300 eur. They work very well with Brio. BR