Long-term fan here. Amplified Heart is the transitional album from when they went from a kind of twee, cutesy Brit-Pop band into a more mature electronica-based act. The husband of the duo, Ben Watt, went through a serious illness and came out the other side a changed man, started hanging out in clubs, getting into DJ-ing and electronica and totally changed the group's sound. If you like Walking Wounded (it's my favorite, too), the follow-up (and final album, I think they divorced), is most similar and called Tempermental, well worth getting. I like a lot of their earlier music, but a lot of it suffers from that tinny cheap 80's production style that can make you wince now. Still, Tracy's voice cuts through all that. Of the earlier albums Idlewild is the best, IMO. There are a million comps out there that can give you a good overview of the earlier stuff (try Home Movies).
P.S. Ben Watt also produced Beth Orton's last album Daybreaker. This is also electronica-tinged folk with a singer whose voice just melts you. Great album, though her previous one, Central Reservation, is even better, very much recommended for fans of EBTG.