I have a friend that is a Manager of a Discount Tire. Shoot me a PM if you want his contact info and he will be able to give you the run down on the positives and negatives of using "Cheaper" brand tires. He will probably also be able to save you some extra $$$.

In my experience with low profile tires on 18 - 19 inch rims the life expectancy of the tires is greatly linked to how often you have them rotated. If you don't rotate your tires every 2K - 3K miles they will wear unevenly quickly. The duration of the tires is also closely linked to their traction rating. Higher traction rating tires are usually softer and softer tires wear out faster than harder tires.

What you mainly pay for with major brand tires is consistent traction in most temp and weather conditions. The major brand tires will usually work better in most driving conditions (Hot, cold, dry, wet, etc) verses the cheaper ones which work really good in some conditions but really suck in others. Most of the cheaper brand tires REALLY suck in one or more driving conditions (usually cold or wet conditions) so you need to be careful about balancing the cost difference with the reduced overall performance.

One thing to keep in mind with getting tires from Discount Tire is that they honor the manufactures mileage warranty. So if you get a major brand tire that has a mileage warranty of 35K miles but it only lasts 7K then you get the prorated mileage difference in price applied to your new set of tires. This becomes a HUGE benefit when you have high performance low profile tires on a performance car which get worn abnormally quickly.

I have tried both major brands and cheap brands for performance tires and you really can't beat the performance of major brand tires in all driving conditions. They are worth the extra $$$.