However, is it worth buying a subwoofer that is more expensive than my
main stereo speakers (the speakers cost £300)

It is the end result that counts.Spend (waste) £250.00 on a rubbish
sub or spend £349 wisely on a quality bit of kit. The choice is yours!

I have to agree with what you said. I am going for REL then
Thank you everybody for all your messages!