$650 is a lot to work with, I could build at least 4 systems with that much money. Tomatoes are tricky... I grew some in a 4" pvc pipe and I never will attempt that again; lots of roots, plugging and backflowing. Maybe a 8" pipe would work but I will only grow them in buckets or 55 gal barrels cut in half.
With pvc you have two methods of growing, NFT and flood and drain. NFT will utilize your net pots and you can grow much closer together then traditional gardening. The pro's are you can keep the nutes flowing past the roots, grow dense and utilize verticle growing. The con's are you are dependant on power and temps can be a big factor.
Flood and drain; by cutting out the top section of the pipe and filling with pea gravel or pearlite making net cups not necessary, but you can still use them. Flood and drain allows more options of what you can plant like some root vegies like carrots and onions. Con's are you are still dependant on power but have a longer grace period. Temps are also still an issue but depending on your medium you can midigate it somewhat. Pro's are the system is heavyer so it will not blow over as easily, you can still grow verticle and still grow denser then tradition gardening.
I will be experimenting with the "Alaska bucket system", not true hydroponics but real close. Maybe an option for those maters
In the pict of the double pvc system, the top is NFT and the bottom pipes are flood and drain.
Just some more examples...
Tracy