Get either a one ohm or a 4 ohm stable amp. Hooking in series will be a one ohm load. But for most of the jeeps for sound quality i'd recommend a 500watt at 4ohms hook them up in parallel and you'll be good. You'll want a monoblock amp
[QUOTE=jeeperjkj;1277307]Two 2-ohms in series would give a 4-ohm load and in parallel would create a 1-ohm load, right? At least that was the way it was back in the day. Did they change electricity?[/QUOTE]
I would personally just get the amp you want, then bridge it, or better yet get a mono amp. Just keep the gain down and don't bump it until you get the other sub in there. once you have the other sub keep it bridged, you don't want a sub on each channel, weird things happen and with newer music most of the low end is mono anyways. i use to have 3 subs running off one bridged am and it slammed.