Things like "grit" can mean different things to different people, but to my way of thinking anyway, pickups themselves don't really have (or not have) "grit". Lower output pickups certainly don't drive the front end of amps as hard, so the "grittyness" that you get out of the amp, and where you are on the headroom curve changes how the amp responds to guitar volume and tone controls... In any case, you may want to throw a good clean boost in front of the amp and see if that floats your boat. It's not exactly the same thing as swapping pickups for something with a higher output, but that may actually be a good thing from what you are describing wanting. A strat, in my opinion, totally needs a clean boost into a JTM45 style amp for example. I don't know how hot the Vela picups are, but interestingly, I never noticed them being particularly low-output.