I have found that a 2800 stall for a mild performance car works well. While it doesnt have an extremely high stall, the perforance you get out of it is wonderful. Just dont buy some cheapo one though.
The correct converter depends on your entire combo. If you have ever called a converter manufacturer to get their opinion on a converter, they will ask you a lot of questions. But for a relatively mild street combo, a 2400-2800 will work well.
Using a C4 you need to be sure you are not cruising under the stall speed of the converter. This will cause the converter to constantly slip and create heat. A trans. cooler will be a must with a higher stall converter.
If using an aod, you can go to a higher stall and not affect freeway cruising in top gear because the transmission releases the converter to get rid of slippage, lower rpm's, and thus get better mileage.
Bigger cam, higher compression, and lower gears (higher numerically) can use higher stall: 3500 and up.
WIth my combo I am going with a TCI Breakaway. It is advertised to stall in the 2400- 2600 range.
Here is TCI's converter chart:
Street/Strip Performance Torque Converter General Application Chart
Torque Converter Series advertised
Sizzler® stock to 260° stock to 3.23 smooth idle, stock comp. ratio 1500 to 1700
1700 to 1900
Saturday Night Special® stock to 265°
stock to 3.23
smooth idle, stock comp. ratio 1600 to 1800
1800 to 2000
Breakaway® 265° to 280°
3.00 to 3.73
fair idle, mild modifications 2200 to 2400
2400 to 2600
StreetFighter® 280° to 300°
3.55 to 4.56
rough idle, large fuel system, raised comp. ratio 3000 to 3400
3400 to 3600
There's a ton of things that will affect your choice, but none of them as important as your cam. Heads and fuel delivery a close second since these will affect the power band of the engine directly.
Weight of the vehicle, wheel/tire size/type, rear axle ratio, and type of driving you intend to do should all have an effect on your final choice as well.