Mac Pro 2008 + El Capitan?

I have a Mac Pro 2008, and I'm looking to potentially upgrade it to El Capitan. Given that it's now going to be a 9 year old machine, will I experience poor performance on such a new OS? Currently I run Mavericks and it's such a smooth OS, however, with the new UI redesign and such I fear that my machine may be too slow. Here are the specs:

2x2.8GHz Quad Core Xeons
32GB DDR2-667MHz
NVIDIA GeForce 8800 GT 512MB
2TB 7200RPM Drive

Thanks!