I have not had the opportunity to sample either model, because my local sony stores no longer put out demo units for these earphones... but I've been planning to buy one, so I've read a lot of impressions on the web.
A lot of Japanese discussion mentioned that the 450/650 sound very different from the 310/510. The 450/650 have a lot more bass. The 650 is very different from the 510. By description, I think it's the same kind of EDM-friendly bass that is Sony's new "signature sound" right now, from the MDR-1/10 to the XBA-H3.
Another common comment is that the 650 have far more treble than the 450. The 450 also sounds competent, but is a very typical, small-soundstage sony affair.
There is a chinese review on the EX650 with some fairly serious testing: http://www.soomal.com/doc/10100004829.htm
The reviewer found it way too bassy, but says the driver quality isn't bad, and recommends that you should use it with bass-reducing EQ. In fact, they suggest that you should not buy if your source has no EQ.
Ardian, between the XBA-1 and the EX450, the EX450 should have much more bass, while the XBA-1 should sound more delicate, refined.