I like the 8" for general detecting, however if you detect just around iron infected sites, then the 5" would be best. But a 5" while searching a field or park can be prtty daughnting.
Like HDRK stated above, it really depends on what type of sites you will be hunting. If you have a trashy area, you'll probably want the 5" coil. If you're still looking for a dealer, I would strongly suggest contacting Tom at Miller MDZ. Look for him in the vendors section toward the bottom of the Forum page.
Sorry, I had to cut my initial reply short before completing it but I was going to add....
With the smaller coil you are going to be covering less area and losing some depth. I have a Compadre with an 8" coil and love it, but I've never used the 5.75 so I really don't know how much better it is in trashy areas. Terry (above) knows his stuff so I'm going to take his word for it.
The kellyco site says for the 8" for more coverage and are hunting a less trashy area. I plan to be in trashy areas. Well I feel that there will be a lot of pull tabs and caps where I'm looking to hunt. So is 8" going to be better or worse in trashy areas??
I found my first silver in about 2 feet of water with my Compadre. Later in the day, I dropped it in the water. Pulled battery quick, opened cover, dried out with handkerchief and went right back hunting. That was 3 years ago and still no problems. My daughter took it over when she moved back home and took it with her when she moved. She has found several silver rings and lots of other goodies. What a GREAT little machine!
I have owned one for 4 years (we had it here in Europe before you guys) and stupidly sold it a few months ago, but at the same time, it was to help a friend getting back to the hobby. It has found me over 10.000 coins in those four years (beach hunting) and got me a fair share of jewelry. You will get 8" on an US quarter, and the unit excells in trash. Be aware that increasing the disc above the 5c setting wil reduce depth.
By the way, the coin of your avatar is well known to me...Found in the US?