The Integra is perhaps the best chassis to put the K20 or even K24 in. They are designed to handle the weight of the K20 and have a taller hood line than the EG so the taller K24 can be mounted without clearance problems.
The K20A is without a doubt more expensive initially. Here's the kicker though, if you take a B18C and stroke it or bore it to two liters, a lot of the cost difference evaporates. Also once you take the B18C to 2 liters you loose a lot of reliability. With header, cams, K-pro ECU, and intake it's not unheard of to get 240hp. And that's with no great loss of reliability. Then there's the K24 block, a sweet bolt on for massive torque gains. Another point is you cannot buy a reasonable 6 speed transmission for the B-series.
The B-series engines have a lot of performance products available for them, but many companies have embraced Hondas new engine and are quickly working to bring products to market. Just think what it will be like in another year when all the companies have released the new products for these engines.
brian g