I'd like to try out a Mod..

[Epistolary Richard]

I take it I need to uninstall BI first?

No, RTW 1.5 and BI 1.6 run in parallel with each other, you can have a mod installed for 1.5 and a separate vanilla version of BI 1.6 (or even a modded 1.6).

BTW, use the JSGME mod enabler programme (link in sig) - easy way of swapping between various mods and vanilla.

you forgot Extended Greek Mod for RTW

Good catch - edited

RTR and SPQR 6.0 look the most promising. I might try Terrae Expugnandae first, though.

I don't believe there's a 1.5 version of RTR available yet. I believe the latest release is for 1.2.