Dead_Reckon...... FYI ....... If the branch circiut breaker is 15 amps ...... that tells me the conductors used on that circuit are probably #14AWG ... (assuming you are in North America ) and probably a R90 temperature rating .......
If you wish to use a 20 amp breaker , the wire size would have to be increasd to #12 AWG ...... and to go to 30 amps .....the required conductor size would be # 10 AWG .....
EDIT: i do know quite a bit about basic wiring, wiring codes, stuff like that, i took electricity and electronics in the 9th grade
With all due respect ..... you must have slept through most of the classes ....... for example you say ...... [highlight]30 amp double throw breaker [/highlight].... No ...its either a single pole or double pole ....... and usually a double pole breaker is used if you wish a 230 ac supply . ( Assuming your house is using a 115/230 volt service )
How do I know is ....... well I spent 20 years in the electrical business.
So please leave any electrical upgrades to a professional .........
dl65 
for one thing, we have always called then double throw breakers, for another, i have wired many things for my self, fans, lights, radios, heck, i rigged fans on my 500w amp (not a guitar amp, 4 channel output, has A and B outputs, am\fm tuner build in, 3 or 4 inputs, 2 outputs, LED display, am\fm presets, i think up to 100, bass, treble, and balance controls) the fans are powered by an old 150w aztec AT PSU, there are three fans in all, one 90mm and two 80's, i mounted them on the top vent grills of my amp, and wired them to the PSU's 12v line directly, works great, keeps the amp cool... and i did not sleep throught that class thank you, i am a bit rusty on terminology, but i can easly dig up old papers if needed... we had to do some basic wiring in that class in a small wooden frame which included:
one light to a switch, and an outlet that ran off of the same power source but was not controled by the switch
two lights that ran off of the same power source, one was controled by a switch, the other by the chain
a setup where we had to have two outlets, and two lights, one light was on the switch, one was on the chain, the outlets where not controled by the switch
and yes, we tested each of these, we did more of them, but i cant really remember all of the configs we did, i do know how to wire alot of things, regardless of what you may think i know, do not assume that just because i do not know the exact terminology i do not know what i am talking about. i know wire is only rated for certain currents, that you get less resistance out of thick wire, all that basic crap, i learned how to calculate resistors also, although that is somthing i would have to look at the color chart to do, i would probably need to re learn the formula's. i am uncertain of the wiring in this house... i belive it may still be the old ball and tube wiring, or atleast some of it, i know it is in parts, i have helped my dad replace light fixtures, and wall outlets in this house, many of them still where on that wiring... this house is over 100 years old after all, it use to be an old farm house, now it is sitting in a suburb that was built on the land that use to be the farm..
EDIT: my dad has done many things in his life, one of them was working for some chain of fast food resturaunts in texas(not sure witch, i would have to ask him), and then he was a certified electrician, he is on disability now, he has a bad back, has several titanium disks in his back, he has done many other things in his life, the last job he had though was in the late 80's or early 90's, he worked for Nissan forklift, repaired the propane modles, faster than anyone else around here could... actually, he was stuck in the nissan forklift building during the flood of '85
