Yeah you can upgrade just the fronts. You do need the full trailing arms for the rear disc swap, and the prop valve too. If you don't want to mess with that just do the fastbrakes front kit. Fastbrakes sells the adapter kit with several options... You can do what I did and get their adapter kit with rotors for $290 with Integra calipers, pads and stainless lines sold separately. Or, you can do the simple $160 11" adapter kit and buy everything else separately, Or.. you can buy the full front kit from Fastbrakes for $575 which includes everything you need. adapters, rotors, calipers, pads and front stainless lines.

You definitely want to upgrade the master cylinder with the larger front calipers. The dx 13/16" isn't going to cut it. A Civic Ex master cylinder is 15/16", and bolts on to the stock booster. $110 from Fastbrakes. You're pretty much looking at a minimum of $700 for 11" front brakes.