not sure about good filter delays, this might be good:

http://www.amvst.com/index.php?name=...ails&id=24

Double Filter Delay effect

i'd say first check these goodies:

http://www.device.arcanedevice.com/?sig_mod

and see if you like any - there's really good stuff there...

this is by arcdev but it isn't on the homepage:

http://web.aanet.com.au/stk/arcDev.Dubb.Box.v2.RC1.rar

for money: audiodamage dubstation is wickeddd