Big HP means big RPM. For a heavy vehicle or a street vehicle that is a no-no unless its just a weekend cruiser.
Big engine means that the same HP is available at a lower RPM with more torque at low RPMs. For example, look at the comparison below. Those two dyno simulations are for a low-power small block, but take a look at them. The two are absolutely identical, but one is a 355 and the other is a 383. The only difference in those two charts is the stroke of the engine.
Same hp, but the 383 makes the same HP at a lower RPM and it makes gobs more torque at low RPMs. Leaving everything else alone and simply increasing displacement will do nothing for HP, but it will increase torque down low. But, you can also use extra displacement (along with cam, heads, compression) to increase HP while keeping the same low end torque. Make sense?
When dealing with heavy vehicles or street driven vehicles, cubic inches are your friend.
And I agree with Cobalt. $1500 is a bit steep.