Is there a stereo amp for under £300 i could add to Marantz Sr7005 to improve stereo music?

?

Speakers are currently just the BX1s but i am buying some more shortly either Kef LS50 or the ATC SCM 11.

I would go for the Dynaudios but can't afford them as well as an amp to power them.

I currently listen to everything on usb flas drives(24 bit flac files).