The two consoles have VGA cables. You can just connect it straight to the CRT's VGA port.
If it's an older monitor and the VGA cable on it is hardwired, you would need a female to female adapter. You get one with the official 360 VGA cable.
The best source for TVs and their input lag recommended to me recently is hdtvtest.co.uk.
It's also worth noting that different input sources may have different input lag on the same TV.
The best two Plasmas in regards to input lag are the Panasonic TX-P50ST30 and the Samsung PS51D550, both...