I used to use Travelocity until recently but I've now started using airtickets.com. I think both have a credit/debit surcharge but none are as high as the "Illegal" one on Aegean's own site.

Most other websites, even the ones that used to charge 5 or 10 Euro have now limited their charges to around 2.5% of the cost in like with the recent EU-wide ruling (I don't remember the exact name). Even Ryanair have limited theirs to 2.5% and if THEY can't get away with charging 8 Euro then you can be pretty much sure it's illegal to do so!

So, for that reason I won't use the A3 site even if it's slightly cheaper (which it usually isn't after you add the extra charge).

I like Airtickets because they clearly display the booking class while you're browsing fares.