[El Sol Infinito]

I've got the typical spongy/stiff brake pedal problem it seems we have all gone through. After bleeding the brakes and checking all the wheels, I'm assuming the problem is now in the brake booster.
I can hear a hissing coming from the back of it when I turn the car off which lasts about 10 seconds- vacuum leak, anyone?
Anyway, I was looking of the Napa website and it seems that some previous owner has already replaced the original master cylinder and booster with what looks to be the replacement setup that Napa's database shows.

Should I replace my current setup with the standard Napa replacement? Should I spend big bucks at the usual suspects parts shops? Should I try to go to a dual master cylinder/proportioning valve setup (safety?)?

What have you all done in the past? My priorities here are to get a well performing, safe brake system first, low cost and quick solution second, and authenticity third.

I've also played around with the idea of putting a disc brake setup on the fronts. I'll probably have to rebuild my front suspension at some point soonish anyway, so why not? However, I'm not going to have the money to do it this year and I need to improve my brakes now. What would be the best way to proceed at this point?

Any help is greatly appreciated.

Thanks,
Bob Asher