Well you've picked odd sizes because it used to be 10gb standard for a hard drive based player but now its 20/30gb. The creative range are good but the Vision M is expensive. If you are not a fashion junkie then go for the Creative Zen which is pretty cheap now and is a pretty damn good player! There are loads of other options including the Sony NW range (I have an HD5 which is excellent although discontinued) but the Zen is good but bulky.
If you want a smaller player of around 6gb or so then you might aswell at least have a look at the iPod Nano (unless you had an iPod and hated it) which looks quite good to me, the iRiver H10 is quite nice too although it is a hard drive based player. I had one but sold it for my current Sony. The H10 had tons of problems when I got it but they have all been resolved now.
The Creative vision m is basically the Creative equivalent to the iPod video (but better imo - e.g. screen). If you don't want to play videos and want to save cash just get another lower range one...if you have the cash to burn however, why not?
One more thing, if you like the Creative Vision M then check out the iAudio X5 which may also be to your taste (I prefer the Vision M tbh).
