Front speakers for upgrading my setup

Currently I'm still using the 5.1 setup with Tannoy HTS speakers and sub that I got as part of buying my Denon x2000 receiver many years ago and decided it's finally time to upgrade.

I saw a good deal for a Kef q20c centre speaker for £120 and decided to go for it. I'm a novice at these things and looking for advice about which speakers would compliment it.

Probably only looking to spend about £500. I saw a couple of R500s within budget but I'm doubting whether I need the floor standing speakers or having bookshelf ones like the r100 would be good enough as I already have a sub which I'll upgrade later.

Similar with the rear speakers, I'll upgrade them next but would be looking for bookshelves. Any advice?