Just my thoughts:

I've never mounted a scope on an AR with a permanent front sight, but I would think that you are correct in wanting to get tall scope rings. However, that will cause you to loose cheek weld with the stock unless you mod your stock. Also, I'm not sure how well you will be able to co-witness with the front sight post, especially to compensate for bullet drop. I would think the best plan of action would be to get a low profile gas block without a front sight (if you feel the need, get folding BUIS) so you will not have to co-witness. They seem to be under $50 at Brownells, I just searched gas block.

Hope this helps!

http://www.brownells.com/.aspx/cid=3...Components/All