The valves won't make much of a difference to the performance on a street engine. At low lift the shrouding on the long side turn out of the intake runner is higher, so airflow will actually be decreased with a BIGGER valve. Big valves only help on higher lift applications or on high-RPM applications where fast, high volume breathing is required. If you're not planning to race it I would stay with the smaller valves, they also leave more material between the valves, where most head cracks appear. Chose a good chamber shape and valve seat shape (maybe try a 30° seat, good for low-lift flow), almost all of the large chamber heads have open chambers with less quench area (that's where the chamber is flat and parallel to the piston and thus squeezes mixture into the main chamber on the compression stroke, this puts off detonation. That's generally not good for performance.
But a couple of questions:
What RPM are you aiming at?
What HP do you want to reach?
Really only street?
How heavy is the vehicle?
Are you interested in mileage?
When we know this we can give you a bit of a better estimate on the heads you want to use. And don't forget, the parts most crucial to performance are heads and cam, and they have to match up nicely. It's easy to get an engine to starve at 3500 RPM, manage 8mpg and reach 200 ftlbs of torque with a set of $ 2.000 heads... But it's also possible to get 300HP out of a set of $ 50 rebuilt junkyard heads, if you match the crucial parts together nicely...
Give us some more info and we'll give you some more help
Max