If you're fitting coilovers I can only advise spending a bit extra. The likes of KW and Weitec (made by KW but galvanised rather than fully stainless) are a safer bet when it comes to comfort and long term durability.
I ran Weitecs on my old mk4 with no problems for a good few years, and that was with them set silly low.
KW V1 are a good price at the minute, and I'm looking at buying a set for my 07 GTI. I've had a good read up and it sounds that just like Weitecs they are very comfortable. And of course if you're planning on keeping the car for a few years the fact that they're stainless is a big plus.
It just boils down to budget. If 300 really is your limit I'd strongly advise against going with cheaper, lesser known coilovers.
KW are more expensive for a reason - they put a huge amount of R&D into damper valving and spring rates on specific platforms to ensure the finished product provides good ride quality as well as the performance and handling improvements.
You get what you pay for.
If you can't stretch to that, maybe price up the cost of a pair of standard rear shocks and a good quality lowering spring set such as H&R or Eibach Pro. Don't be tempted to go lower than around 30/35mm on standard shocks. Too low and the standard shocks will be working outside of their capability, and you'll end up with a bad ride and reduced life of the shocks.
Remember, buy cheap - buy twice.
Hope this helps!
