JJ is very correct.
I have done a lot of suspension setups over the years, mostly offroad and street but obviously the principal still applies.
What I do know about the cheaper brand stuff is that when the deal seems to good to be true, it usually is. When I went for the cheaper stuff it always wound up biting me in the arse later down the road. Initial impressions were usually good but after some use they usually degrade rather quickly. Springs soften, dampers not matched to springs, valving incorrect, blown seals and even bent shock pistons. Rebound and compression not correct stroke being set too short or long.
The reason why they are so cheap, compared to others, is because they cut corners. I would recommend springs on stock struts before cheap coilovers.
Suspension is one of the points you should always try not to skimp on. Save your pennies and try for a brand with a better/longer history.
If you can afford 800-900 then your already halfway to a better quality coilover.