Epilogue is by far the best instrumental. Silhouette is very nice but it never stuck with me. Here they are in order of my preference
Epilogue
Ending Credits (almost as good as Epilogue)
Requiem (mainly for the part that got stuck to TAIT, that is AMAZING)
Patterns in the Ivy (I love the piano in it)
Silhouette (err, how is this more musically challenging than Epilogue? Perhaps more complex, I'll give you that but Epilogue takes true talent to play)
Madrigal (pretty boring... but better than the others)
For Absent Friends (yawn. again, pretty boring, but it's worse than Madrigal becausse it's less dynamic)
Prologue (what the fuck? Who voted for this?)