Compression makes all the difference in the world.
My dad had a 1978 440 that he built up to replace the 68 440 that was in his Charger (it burned a quart of oil for every mile you drove), had ported 906 heads, Mopar performance cam, Edelbrock torker intake, long tube headers, and just about everything bolt on he could do to the motor. It was lame.
He said that, even after he did all the to it, it would hardly spin tires. The 68 440 actually ran much better...would spin tires through 1st and part of 2nd gear, stock.
So, he looked into it, come to find out, the 78 440 had 7.8:1 compression, whereas the 68 440 had 10.5:1.
So, just a couple points of compression can outweigh headers, a cam, intake, heads, etc.
So, I'd say research how far you can go before having to worry about valve clearance, and go from there. I've heard of people putting pretty high compression flat tops in these motors, so, I'd think you'd have a bit of wiggle room.
But, after my dad's realization, he had the 68 440 freshened up (turned out the valve seals were bad). But, he had the heads from the other motor shaved, and had the block decked, which upped compression to 11.5:1.
So, I'd definitley look into it if I were you. Unless a supercharger is in your future, than I'd actually look at going the opposite way.
Also, keep in mind, you'll have to run higher octane gas with a higher compression ratio.
But, basically, upping the compression makes more use of all your other mods. Your basically adding a couple pounds of boost when you do this. Just, its always there and theres no lag
And, on turbo/supercharged cars, adding 2lbs of boost makes a power difference. Well, one point of compression is a couple pounds of boost. Its not a 1:1 ratio. So....as I said, you'll notice it I'm sure.