Most amps are not recommend for 2ohms stable load in the bridged mode. Hooking two 4ohms sub in the bridged mode. The amp will see a 2ohms load. It will push more watts into a 2ohms load but it will also produce more heat in the amp and could fry the amp. That being said sometimes amps will work bridged in the 2ohms mode and not fry. But to be safe keep the ohms at 4 when the amp is bridged. Now I have my amp bridged with two 4ohms MTX-RT10 subs. They are wired parallel so the ohms drop from 4ohms down to 2ohms. It gets hot but I have had no problem with it. My amp is a older one so that could make a difference.
You can also hook both 4ohms subs wired parallel that will make the amp see a 2ohms load and hook them to one channel from the amp. This way you will get just about the same watts as bridged and will be safer for your amp. Also with two sub it will have more SPL.
What model of amp? You MIGHT be able to bridge pairs of channels so you'd have 100W?? X 2 channels @ 4 ohms then run each one to a voice coil on your amp.