As a general rule of thumb with detectors (and I've owned just about every one of them on the market to date) here's a few basic rules:
1. If you are wanting to keep it simple and probably not going to use a whole lot, you don't need all the target ID stuff and such. A simple turn on and go Tesoro will be sufficient.
2. If you are going to be coin hunting in like school yards and parks, something like the Ace 250 or F2 or F4 will be really good. The Minelab X-Terra 30 is probably the better of all those for that type of hunting. With the X-Terra 50 being more expensive but offering more bank for the buck.
3. If you are going to be relic hunting for Civil War stuff and alike items, than depth is more important than ID and all that stuff. There are a few units I would recommend for it, but some of the higher end Tesoros are great for relics and relatively cheap in price. Most people these days are hunting with either a Whites MXT, Fisher F-75, Minelab Explorers, and Nautilus IIbs. They all pack very hard punches but the F-75 is the latest and greatest that is getting a BUNCH of great reviews right now. I just committed to buying a used one myself. They will run you around $930 new but I got mine for $650 used.
Hop over to
www.thetreasuredepot.com and check out their classifieds. They do a really good job of weeding out the crooks and you can find really exceptional units for great prices. Detectors don't retain very high resale values and most guys will try one out for a while and sell it to get something else to try. I've got many almost brand new machines for $300 less than they cost new.