#1
Ok so ive been doing some reading but i just want to make sure. I have a 140 watt and 8 ohlm Marshall Cabnet That i would like to buy a head for because i currently have a Kustom Head that you have to run pedals through, that is 200 watt and 8 Ohms, so when i buy a head what Wattage and how many Ohms should it have.

Also can someone just give me a general Rule of Thumb when dealing with this kind of stuff. Also if you have any Spacific Heads that you think would work good thats within 300 dollars, that would be great.
#2
Cab should have a greater capacity (watts) and equivalent ohms.

Or conversely, the head should put out less wattage and be capable of connecting at equivalent ohms.

What you should actually buy is dependent on how you want to sound.

Go the the "Guitar Gear and Accessories" forum and ask your question there, with more detail as to how you want to sound, what gear you currently have, budget (as noted), used or new and your general location.
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Charles Darwin