I play a Yamaha 475, which is an intermediate student level instrument. Any of the Yamahas above this (budget permitting) would be a decent buy. Other good makes to look at (which I would be now if I was looking to upgrade further) are Trevor James, P. Mauriat, Yanigasawa, Cannonball, Keilwerth and of course, Selmer. I'm told that Hanson also makes a good sax, but it's a brand I don't know too well.
Pro sax players are usually expected to double on flute, and I know at least three ex-flautists who have, for health reasons, made a successful switch to saxophone. The fingering is similar although the embouchure and technique are, of course, very different.
Best to start with alto or tenor saxophone - that's really a matter of preference and physical make-up. If you're capable of man-handling a tenor and that's what you fancy, then go for it. I wouldn't go for a soprano or a baritone until you've had at least a little experience.
My saxy friends and I find sax.co.uk a decent company to deal with:
http://www.sax.co.uk/ They have shops in East Sussex and London and are very helpful people.
I would suggest you try a rental deal to start with, and get yourself at least a few lessons in order to learn the basic techniques. After that (and as a grade 8 musician you don't need me to tell you this), find a band to play with.
If you'd like more advice than this mediocre player can give you, try here:
http://cafesaxophone.com/forum.php .
And finally, welcome to the wonderful world that is the saxophone. ;-)