Don't think you can player enchant those mechanical crossbows from DR. They do sell a 6x version, though.
Thanks to those who tried to help with opinions and advice. I decided to go with BriarFox's advice and throw some sighting on the crossbow.
The only real example where I can see the difference is the Arena. Where I am assuming the creatures are a little older as the matches progress. Shooting bow on eye first 4 per group and then head and eye on champions. I averaged 4:30 per run. (having misses on eyes is the largest factor for me in having slower arena run times)
A perfect run, with no eye misses was 3:52. So for me, I am adding sighting to my bow as I had none during these arena runs in DR.
Aurach
It's 5x, max light, and T1. It will cost around 22k BS to get it to 150 services (and 2 years), so yours is cheaper. All I would lose is one ensorcell and the trips to the merchant to lighten, which isn't bad.