Just thought I share my experience as I'm well chuffed.
I was running an old DSL-504. Working ok and had been for years but the other day I put my phone number into a site and it said I should get 7M which I wasn't. So I risked 15 quid on a TP-Link TD-8840T to replace the DSL-504. Sync speed on DSL-504 was 6624 Kbps, IP Profile 5500 kbps. On 8840T sync is 7616 kpbs and after a week my IP profile is now 6500 kbps. On speedtest.net the best I used to get was 5.05M, today I got 6.20M. That's 23% faster for 15 quid .
I've also asked my ISP to turn off interleaving to see if I can get 8128 and thus a higher profile still. The exchange in not ADSL2 so until (or if) that happens that as best as I can do.