Got the amp yesterday and got it put in. Its more work though than just rounding out the corners. The overall amp dimensions are slightly different. MK2 amp is 10" Hx 10"W, MK1 amp is 9 13/16" H x 9 13/16" W. So a good bit of dremeling was required on one side and bottom to make this fit. You also had to make small cutouts for two parts on the left side of the amp. It mounted up fine although my dremeling doesn't look the best, but not leaks of any kind at amp or woofer.
On setup, its either clear that my amp was crapped out or this new amp is much stronger. Either way to calibrate at 85 db at 0 on receiver only .25" above first tick is all that is needed. Subs sounds great again finally and should last many more years. Also, running both subs I'm pretty flat from 80 down to 20, with a slight dip at 25.
Its a upgrade worth doing once your MK1 starts to fade.
A wise man once said if it sounds like a broken record there is a motive behind the message.