At what point would you suggest Aftermarket Axles.

I think there's an axle rule for slick tire cars. If it was me, I'd say once you need a roll bar (11.49 and faster) axles are a good choice. If a spool is used instead of a differential, axles are mandatory. For your car, good brakes, a solid front suspension, and a driveshaft loop would be all I'd worry about having. They dont mandate the loop either, but I think it's cheap insurance. I've had slower cars spit Ujoints before.