I'm a huge fan of Southern Polyurethanes. Compatible with just about every single brand of paint and you cannot beat their prices for the quality with their primers and clears. Ships to your door free too.
Etch primers are typically used over aluminum or in production shops where they are under the clock to get things in and out rapidly such as insurance/collision work. Epoxy is the way to go if you have the time and you will not be disappointed with it. Plus it doubles as a final sealer before your base coat with a little reduction.
Just my two cents.
