Yes, they're perfectly fine. I believe Premium is the next level below Super Pro.
Duramith
Super Pro
Premium
Premier
Standard
Seyberts is a support of AZBilliards and I remembered offered competitive prices. That being said, maybe the market price on Aramiths have gone up, but double check with other vendors to be sure.
Good balls.
Here's another option: http://www.ebay.com/itm/Belgian-Aramith-Premium-Pool-Balls-Best-Value-in-Balls-FREE-US-SHIPPING-/221350544207?pt=LH_DefaultDomain_0&hash=item338985434f. Joerackem (no affiliation) has a pretty good reputation around these parts as well.
I just got the pricey Aramith Tournament set for xmas. I like them fine. Now I rotate between the Aramiths and Centennials.