I'm fitting a stealth sub to a mates A3 and just using the rear pre-outs to feed a 4 channel amp. The amp will power the sub on 2 channels bridged and the other 2 channels for the rears (as the stock amp powers both). I usually use F405's which have a selector to feed the input to channels 1 & 2 into channels 3 & 4 as well, therefore negating the need for Y splitters. The F400 doesn't have this but it does have it's own pre-outs (ch1+ch3 and ch2+ch4) detailed in the manual for linking to a second amp. If I link this output back into ch3 and ch4 would this present any problems. I know it works as I've tried it, just concerned about the long term effect as no where in the manual/web does it show this config. Or should I just stick with Y splitters?