Which cam = more power

I am in the process of building up my bottom end (306) and was thinking about swapping out the cam. I have cnc ported e7's with larger valves, edelbrock performer RPM intake(soon to be ported),1.6 RR, 70mm throttle body, bbk headers, 24# inj, and 10.5:1 compression. I currently have a comp cams extreme energy 270hr. Specsur@.050-218int/224exh; lift 512/512. I was looking into an X-cam Specsur@.050-224int/224exh ; lift 542/542. Do you guys think this cam would work well( make more power)? What about drivability, I have a 5 speed and 3.73's? I will be using speed pro forged pistons, block deck milled 5 thousandths, heads milled 40 thousandths, do you guys think there will be piston/valve clearance issues? Thanks in advance for any advice- this will be my first high performance bottom end build up.

And the cam, do you think it will be worth the $165 in terms of HP increase?