I was one of the first to have a 3090 when it was first released in the UK (95 i think) and have also owned an A2.
The 3090 was the top of the line machine, with many great features, and it sounded like a top end machine. The A2 had dts and a few more of those DSP programmes, but was too under powered for my liking, but a great sounding machine that was very similar to the 3090.
If you are a Yamaha fan, i would suggest a used A1, AX1 which can be picked up from £350-£650 on the used market, don't pay anymore! These are better spec than the A2/AX2 with that extra power and more like the 3090 you have at the moment.
However if you are changing just for DTS i would proberly think twice, the 3090 is still a brilliant DD amp that many today will have trouble bettering.