I went from the series 1 Pioneer speakers to the Wharfedale 10.2's. The difference was obvious, as I was able to hear things I hadn't before with the Pioneers. The soundstage is great, and they easily fill my large space with ease. It feels like music is flowing over you from all directions, rather than coming straight at you.
I still have a pair of Pioneer bookshelf speakers as my surrounds, and I much rather listen to music/games in 2.1, as the Pioneers just feel harsh to empty now.
As for the Kef Q300's, those too would be a good choice. I've never heard them myself, but from I've read on them, they may be a bit better than the 10.1's. They may be more on par with the 10.2's in terms of overall imaging, but again, I've never heard them.
Sdg4vfx's comment about SQ and imaging is spot on, I think. EQ can help balance out any tiny SQ issues you may find with some speakers, but the speakers ability to build an enveloping soundstage can't be EQ'd in.
You can also look at the Focal Chorus 705V's at musicdirect.com. Any of these speakers would be an upgrade over what you have, and should really make you happy. Just need to see which you prefer.