darshevo, you are incorrect when you muse that getting a different coil, would enable you to swap venues, and pursue prospecting (I'm assuming you meant nuggets, in their natural state, when you said "prospecting"). The coil size has nothing to do with that. I mean, within each type detector (coins vs nugget machines), there may be benefit, within the chosen machine, to 1 coil size over the other. But to simply have one coil that finds nuggets, verses another coil on the same machine that doesn't: no, it doesn't work that way.
The 2 goals (coins/jewelry/relics verses nuggets) are two opposed types of hunting. Nuggets in their natural state are most often pinhead and grain-of-rice sized (even down to pepper grain size!). So machines designed to find items this small (in the accompanying mineralized soil where nuggets naturally occur) are designed from the ground up, for this exact purpose. Contrast to a coin/jewelry/relic guy.... who DOESN'T want to hear every little fleck of birdshot, every staple, every straight pin, etc...
Yes there are machines designed to be able to go back and forth between each goal. But they will excell in neither arena. If you absolutely must have one that can do each type, you might consider the MXT. But otherwise, get one for each purpose. A good coin/relic/beach machine under $1k, if you are a beginner, is to look for a used 6000 Di pro. Or if you want a little more bells/whistles/depth, and want to spend a little more, and spend more time pulling your hair out a little more in a learning curve, you can find an Explorer on ebay usually for under $1k