Test is proposed to change next year. MCN were highlighting it over last while. Have attached a link on to the Driving Standards Agency info on the new tests. Appears to be October next year.
http://www.dsa.gov.uk/Category.asp?cat=405
Do it as soon as possible!
Depending on your age ie if over 21 you have option to do a DAS course which avoids the 2 year restriction.
As for restrictions I know loads of bikes can be restricted to the 33bhp, I think you get a certificate to prove the fact should you be stopped. Can still have a lot of fun on a 660/650 even if restricted
Although I passed my DAS test a couple of years ago I haven't had chance to ride much since but know that Suzuki's SV650 is an extremely popular first big bike both in restricted and unrestricted form. Suits both new riders and more experienced ones,still gets rave reviews.
www.sv650.org is a cracking website and the forums will give you loads of info from folk who have ridden with restricted and subsequently unrestricted bikes so they would be able to give you info from 1st hand experience. Well worth a look and popping a question or 2 on there.
Good Luck with the test