Check out this website,
http://www.homecnc.info/cnc-main.html
I don't know much about servos, other than the motors,encoders, controller, add up to about $1000 minimum without the mechanical part of the machine. That's why I stayed away from them.
Check the classifieds on this forum. Balsaman is selling his 2nd servo router for about $2500. Read his thread on building the machine. Its one of the best ones here.
To my knowledge Autodesk inventor will not drive a CNC machine directly. It just CAD. Once you export in DXF format (for example) you usually need another program to take this drawing and produce G code to run your machine.
www.sheetcam.com would work. Then you need a program like MACH2 or TurboCNC to read the G code and control your machine tool.
I just pulled the $1000 out of the air. You can build a unit for $500 for sure.
Use stepper motors.
Don't expect high end speed or cutting power. If done properly, you should get good accuracy however.
You had a pretty reasonable machine, (costwise) until you mentioned cutting 1" aluminum. That requires heavier cutting forces than some of the other materials you want to cut.
Good luck.