don't forget to check
www.soundonsound.com - the reader ads section is chock-full of goodies and because it's really audio-orientated you get people who know their shit and look after their gear!
i listened to the following active monitors:
Alesis MkII
Rokit KRK-6
Yamaha MSP3
Tannoy Reveal
Wharfedale Diamonds
and i ended up getting the wharfedales... they had all the clarity and good high-end definition of the yamahas, but with less brutality... definitely had stronger and clearer bass than both the yams and the alesis, which were ever-so-slightly muddy. they are fucking loud, but tbh that's not important because now i can monitor at lower levels.
it really does depend on your ears and your heart. judging which monitors will wear your ears out quickest is really tricky... that's one of the things that made me think twice about the yamahas (my intended choice). they were so harsh and brutal in high-mids that i don't think i could use them for very long...
...the problem with buying monitors is that you never know what they'll be like to live with. unless you are fabulously wealthy this means you'll probably make your choice based on 10 mins of listening in a music shop...
just go along somewhere and take 3 good CDs with you that you know really, really well. i took rage against the machine's debut (beautifully mixed/mastered), a great recording of a sibelius concerto, the first rinkadink album (for bass-heavy techy stuff) and some of my own tunes. i thought i would feel under pressure to choose but the people at the shop were most kind and basically left me to it.
good luck!