The first half of this is true, but you cannot increase a flash's power by changing the bulb. It's the quantity of capacitors built in that defines the energy storage.
Originally Posted by Mainecoonmaniac
But certainly 2 of 200Ws is enough to get started, more than enough for 35mm and OK for many purposes with medium format. It's only LF where it would struggle.
I will disagree with MattKing and strongly advocate the use of a DSLR for metering, if you have one already. If you set it up correctly (absolutely no dynamic-range-adjusted modes, M exposure), it can give a very accurate indication of exposure, especially if you look carefully at the histogram. The greatest value though is in visualising how the light falls on your subject, which can be a bit difficult initially with flashes. A flash meter is also highly valuable but they're not cheap.