One of my 6870s is from Sapphire and let me share my experience. They are cheaper than brands like Asus, MSI or HIS but their build quality is very good. The best thing is even their base models come with Custom Cooler design with Copper heat pipes, resulting better cooling than the base models from other brands. So a good degree of overclocking is possible with it. Currently this model is available within 10.8K to 11.2K. In CosttoCost site it is listed as 10.2K only.
Regarding their after-sales service, they are far far better than Asus (the notorious Rashi peripherals)....I can't comment on MSI service. When my card went kapput due to high voltage fluctuation and without using a UPS, I called out the shop from where I've purchased it. They asked me to come at a particular day and the card was replaced within 1.5 Hrs on the same day only.