I have a Giant TCX Rabobank and I find the braking performance lacking.
If I put V brakes on the bike, will the stock levers pull enough cable to work effectively with the stock levers?
No. You can either fit Vees using a "travel adaptor" or you can fit a fork mounted canti hanger and tune your brakes (search this forum for threads) at which point your cantis will feel like hydraulic brakes. No one knows why bike makers don't fork canti mounts as standard - its one of those mysteries. Either way you should probably fit Kool Stop pink or Swiss Stop green brake pads.
Before giving up on your current brakes, try shortening the straddle cable as much as possible.
I like this Jagwire cable hanger:
You simply tighten it with an allen wrench.