Yes they sound different because usually they have a totally different amp connected to them. They each have their supporters/detractors. Some designs have way more selection as well which makes them more popular. The EL34 seems to have loads of different options while the EL 84 is rather limited. EL 34 and 84 are pretty cheap though at $10.00 while some of the 2a3 300b I see for $300.00.

Antique Sound Labs for example has the cheaper tube amp the MG 15 Si but it uses a tube(KT 88) that is more than double the price of the EL 34 used in the AQ1003DT. Pay a $100.00 more for the amp but save way more in the long run...Plus UHF said the AQ1003 was better - I would probably agree but didn't hear em side by side.

The EL 34 are usually in amps of 30+ watts better for tough to drive speakers.

I have to laugh have you read the thread on Speaker asylum? I don't get why some don't believe him on the bass output of the AN E D. I thought it was kind of neat that Peter would actually take his wares to the guy's house.