07701 is DOE climate-zone 4, so according to the Building Science Corp data you won't need to use a vapor retarder with open cell foam the way you might in a colder climate. (See page 16 & figure 10 of the "Understanding Attic Ventilation" document.)
According to the Oak Ridge Nat'l Labs estimators come up with a minimum attic insulation of R38 as cost-effective retrofit for any 077xx zip codes, even with high efficiency heating & cooling equipment. (Check it yourself here:
http://www.ornl.gov/~roofs/Zip/ZipHome.html ) I'm assuming you have at least 6" of something (batting or blown) on the attic floor already(?) If you go to an insulated rafter configuration DO NOT REMOVE the existing stuff (even though some foam installers will tell you to "...because it's no longer necessary....".) The total R-value (rafters + attic floor) still counts- particularly during the heating season.
With the ducts & air handler in the space between insulating layers (roof deck/ducts&AH/attic floor) it's then only semi-conditioned space from an insulation point of view, but with a sealed attic it's fully within the pressure envelope, with at least R19 between the ducts/air-handler and the 100F+ roof deck, which is way better than having it outside the insulation & pressure boundary. The difference in cooling efficiency fully vs. partially within the insulation boundary might be measurable, but would be mostly an academic exercise, and reducing the full R-value doesn't gain you any cooling efficiency even if it reduces the ambient temperature surrounding the ducts, since that lower ambient would only be lower because it's now full-conditioned space- an extra direct-load on the AC. But difference in heating performance would be dead-obvious on the bill. Only remove insulation where it would interfere with installing the foam (like pulling it back from soffits 2-3' so they can get a spray gun in there.)
You probably arleady know that NJ gives a kickback for high-efficiency cooling equipment like yours (not much, but it's probably worth filling out the forms.)
http://www.dsireusa.org/incentives/incentive.cfm?Incentive_Code=NJ10F&re=1&ee=1
They also subsidize better-than-average energy-audits (which might point you to the most cost-effective paths for reducing the overall heating/cooling loads.)
http://www.njcleanenergy.com/residential/home/home
But NJ doesn't subsidize insulation as extravagently as some states, but there's something:
http://www.energyfinancesolutions.c...rmance_jersey/eligible_measures/building.html
NJ does subsidize air-sealing fairly heavily if the heating-season performance exceeds 25% reduction (which it just might!):
http://www.njcleanenergy.com/reside...rformance-energy-star/benefits-and-incentives
Odds are pretty good that your attic floor/conditioned space boundary is leaky enough that you can hit that 25% estimated heating savings on the air-sealing & insulating aspects of going with a foam-insulated & sealed unvented attic. You may need to foam-seal the foundation sill as well to hit the magic 25% savings mark for the since it's usually one of the largest air-leaks in homes, even new ones. But that's typically only ~5-10% more foam, and at a favorable price if done on the same day as the attic. (It's cost-negative, if that's what gets you over the 25%-heat-savings hurdle for the 50% of up to $5K cash rebate.) It's probably well-worth the cost of an energy audit that utilizes a pressure-door test to find out!
Based on what I've seen on other retrofits, sealing up the attic with more insulation will reduce your cooling load enough that decommissioning (& sealy up ) the whole-house/attic fan is the right thing to do, especially in higher humidity climates like the Jersey shore, where latent-loads (humidity) accounds for more than half the load, even in the cooler shoulder-seasons. Running a slightly under-sized to right-sized high efficiency AC system will use less total electricity, and provide more comfort (by drying the place out) than sucking in higher-humidity night air with an attic fan. Sure, the compressor & air-handler may use 10x the power of a whole-house fan while running, but it'll run a far lower duty cycle to achieve the same amount of sensible (temperature only) cooling as the attic fan, but will be lowering rather than raising the indoor relative humidity in the process.