If this is your first experience of racing, I'd advise against throwing hundreds of pounds at this. As Si said the value of something is not in its price, its what you get out of it. As such the top line branded stuff, whilst being fantastic, you aren't going to extract that performance.
I'd advise you have a look at this link.
http://www.oople.com/forums/showthread.php?t=145946
This is a local racer, you'll likely see him at Bury, who's used budget gear instead of the Orion and similar stuff. His comments are interesting, but even more interesting to you. The speedo he's got is £28!
My lad has recently started racing and I got him one, and a Hobbyking motor. Both are amazing. And I'm not saying for the money, they're good, I'm saying these things complete. At my local club, Ribble in Preston, these are appearing everywhere.
If you want some more information, watch this, especially the part comparing the unit to an Orion at the end.
http://www.youtube.com/watch?v=nRMoj1WDyEs
Just one mans opinion but I'd be looking at these. Best of luck with what ever you go for. Hope to see you racing soon.