offroad lights

Ok, the harness you have most likely was set up for 55W bulbs and 16 GA wire. It's great that you installed a Blue Sea block, that's the 'proper' way to do the wiring. Each of the runs from the lights back to the block/relay (assuming you mounted your block over the left fender), is going to be what, 6 feet long or thereabouts? The proper way to look at it is to know what amperages you can safely push through what GA wire for however long your wire run is. Your 2 100W bulbs calculate out to 16.66 amps (2x100 divided by 12=16.66 amps). The longer the run and the higher the amp load, the bigger your wire need to be, you can mitigate this with lights since you have a pair of them. Running too small of a gauge wire for the amp load results in two things, excess voltage loss and heat, both of which are bad. A common way to think about it, is to think of the lights (or accessory), "pulling" or "drawing" amps from your system in order to work. You hook up a pump to too small of a hose and you can't get the pump's potential through that hose, same thing with electricity.
With what you are suggesting and assuming the harness is most likely 16 GA, technically speaking, the answer is yes you could run two 100W bulbs through 16GA wire as the way it would be done is to wire the two separate leads together at a point that would leave maybe a 4 ft (single), wire run to the relay/block. This calculator i dug up http://search.yahoo.com/r/_ylt=A0oGdS_tSipR92gAuK9XNyoA;_ylu=X3oDMTEyZ2ExamRtBHNlYwNzcgRwb3MDMQRjb2xvA3NrMQR2dGlkA0RGUjVfODE-/SIG=11s6cu8pg/EXP=1361754989/**http%3a//www.powerstream.com/Wire_Size.htm has a rule of thumb calculator in it. enter the values (12 VDC, 8 foot run (expressed as one way circuit calculated as a round trip so double it), 16 AWG, Max Amp load (16.66) and it spits out the voltage loss. For your application, under 6% voltage loss is considered reasonable, under 3 is awesome but not totally necessary as off road lights are not a 'voltage range' critical thing. If you tinker with the values you will see that if you 'oversize' your wires, the voltage loss drops considerably, this also results in less heat, which is what you want. If you were to run two 16GA wires instead of two going to one, then that would be better. You're leaving plenty of 'room' amperage wise to be safe.
I went over the top and over engineered it, not being an electrician but being totally paranoid of knowing just enough to possibly do something wrong and fuck up my truck, I used all 14GA individual leads from the lights. In your case, two 16GA should be fine but two 14GA will lower your voltage loss and the lights will be closer to their max rated output, not a huge amount more but a little.

 

Bro that is a sick light set up. This web site is so bad for my wallet haha I NEED IT ALL

 

Thanks acdronin, that all makes sense.
I'm probably just going to run my own wires, as it's pretty easy to do and I'll know what current I can handle if I go with larger wattage bulbs.

I've wired up relays for my other lights but I can't seem to remember...
When you run two separate wires from the lights back to a relay, you'll still be attaching both to the same pin, correct?? You'll just be crimping them together at the end to slip the connector on to attach to the one relay pin??
As opposed to wiring them together and running one single (4' as in your scenario) back to the relay pin?? I don't ever remember a relay with two separate output pins....

 

One of mine it's crimped together at the pin, the other one has two output pins, you may have to dig around a little but they can be had.