A dual brushless setup is mostly bling and or novelty. A single motor/esc weighs less, is less complicated and is def faster. You need to decide if you're going to stick with a dual. If thats the way you decide, then just get another VXL, but consider buying new and staying away from trouble.

The Castle 2200 Combo is a proven setup in the Emaxx (brushless Emaxx uses that setup) so consider going that way if you decide to simplify. You couls sell your working VXL and put it towards the 2200 setup.