Well you are true to a certain extent to the Lag aspect however it can be taken care by sizing the turbo correctly and it is not true that the BHP doubles at 14 PSI it varies from engine to engine and turbo to turbo.
As for the turbo kit I came across a nice kit from a company named
5150 autosports
Address: 1348 arrow hwy g
irwindale, CA 91706 US - map it
Phone: (626) 359-9572
Fax: (626) 358-7801