building a real time analyzer

so im thinking of building an RTA to help adjust sound systems properly. has anyone else built or used one? do you think that tuning based on the RTA sounds better than tuning by ear? if i do end up building one, im looking at cheap, as i dont think theres a reason to go too advanced. im looking at the berringer ecm8000 mic, and my laptop with True RTA on it. im not sure if i should go with just a basic phantom power unit, or a full mixing board. <a href="http://www.guitarcenter.com/Behringer-MICROPOWER-PS400-Phantom-Power-Supply-336830-i1129177.gc">phantom power</a> <a href="http://www.guitarcenter.com/Behringer-EURORACK-UB802-Mixer-102331477-i1153481.gc">Mixing board</a> i dont know if theres a need for the latter. also my laptop, or rather netbook, only has one shared jack for line in/out, so im going to go with a usb sound card as well. any input on that? ive also seen phantom power units that hook up with usb directly, would that kill 2 birds with one stone? any input is much appreciated. thanks

guess html isnt allowed http://www.guitarcenter.com/Behringer-MICROPOWER-PS400-Phantom-Power-Supply-336830-i1129177.gc phantom power http://www.guitarcenter.com/Behringer-EURORACK-UB802-Mixer-102331477-i1153481.gc Mixing board

The Behringer mic coupled with a laptop running TrueRTA describes my RTA. although I've since upgraded the mic.  I use an M-Audio USB external sound card (the MobilePre) that includes the required mic phantom power supply.  No need for a mixer.Support the12volt.com

so does the mobile pre actually act as an external sound card? $150 for phantom power + external sound car isnt bad, but i could bet that mixer for 50 and a sound card for 30ish. or better yet if i dont need the mixer at all then 30 for the sound car and 20 for a phantom power supply. so the question is what do i really need? is it worth it? i just calibrated the 1/24th version of RTA on this desktop at work with the built in sound card and got a flat response. so im thinking a high quality sound card isnt as big of a deal as some would say.