Irrespective of your preferred cadence, installing higher gears will not increase your speed, unless you physically cannot pedal fast enough in your current setup. Gearing only affects the amount of pressure you put on the pedals, not the power you transmit to the wheels. It is an incorrect assumption that riding in a higher gear one will be able to pedal at the same rate and therefore go faster. If that were true why would you ever be in a lower gear?

On rails to trails conditions, such as a crushed limestone path, that is unlikely to happen unless you pedal extremely slowly. In the 42/11 gear at only 60 rpm you are going almost 18 mph, which is quite fast for those conditions. 70 rpm is still not very fast pedaling and would get you 21 mph.

In any case it appears that the crankset you are considering will also require a different BB, as the OE crankset took a longer spindle.

NOTE THIS ENTRY FROM SHELDON'S SITE:
Acera-X M290 Triple 110-113 Square 47.5-50 Recalled! Do Not Use! See Shimano dealer for free replacement. Compact 1995

p.s. It's pedaler not peddler, unless you're talking about there rate at which you sell stuff.