Hey, thanks! The tubes looks as though they may need a bit of maintenance. Are they any alternatives on the same level as the Woo that are solid states?

Hi,   I am hopefully going to buy a S/H pair of HD800 and was wondering what a suitable amp would be?  I don't want to spend more than £650 (S/H or new) and I'm based in UK if that makes a difference.   Thanks in advance!