FWIW, we don't use lightweight alloy pulleys on high output engines.
What we do use are dampers by "Fluid Damper" & "ATI Performance Products"
Both are extreemly effective removing torsional crankshaft vibrations.
See these sites: http://www.fluidampr.com/ and http://www.atiperformanceproducts.com/
I won't say that one is better than the other as they are both top shelf products.
I do like the 360deg lazer etched timing marks on the ATI damper, as it makes cam timing a breaze.
Though more so on nissan engines than Honda engines due to difference in camshaft set up procedure etc (Sorry - I have digressed)

IMO, if the engine is near standard.
There is little to be gained changing to an alloy pulley.
Give it a go if you must...
But be aware, you may simply be convincing yourself in your mind that this was a worthwhile modification. When in actual fact there is little to no gain at all. That is, IMO the perceived gain would be quite difficult to measure is real terms.
Example. What time is it worth on the 1/4 mile?
I'd say 0.05 ~ 0.1sec if you're lucky.
Should that be the case, is it really worth the bother?
Also of note... Alloy pulleys are banned in import racing in USA.