What router and what to do..

Hi all and thanks for that page.

Let's see if someone can help.. I'm living in countryside with a bad and slow connection with doesn't allow me to confortably stream vids.

Anyway, I'm on ADSL2+, 8.5 Mbps real instead of 10Mbps from contract with my ISP. No upgrade are possible with my ISP because of a downstream line attenuation of 25.0 db.

The modem router I have is a free one delivered by my ISP, does it worth to buy a new one ??.. Eventually change the firmware and pass tomato or wrt ??.. 

Thanks.

George