I did not like the stock slimline coil that came on it. some people liked it..and some didn't. I absolutely love the 6" excelerator coil...but if you already have the 4.5 x 7...there really is no reason to get the 6". I don't know what settings you are using..but the 4.5 x 7 coil hit silver dimes for me from 6" to 7" amidst trash....it's a good coil.
The 10 x 14 excelerator is an absolute killer...but gets a little heavy after a few hours. Once you hit a silver dime at 9" or 10" with a nail or other trash item in the hole though...you won't care about the weight

It also separates better than any other big coil I've ever used...hands down.
Right now I first pound a site with my ex2 1050 coil...then repound it again with the 10 x 14 excelerator...then pound it for a third time with the 6" excelerator coil.
I don't use an 8" coil...but there are a couple of good ones...the minelab...and the sunray.
James ND also always has tons of great finds with the Joey coil. That is another good coil and I did have one of those for a while...but always came running back to my 6" excelerator. It separates like a 4" coil but gets the depth of a 10" coil...so what more could I want? The only reason i don't have it on all the time is because sometimes the area is just too big and i need to cover more ground per sweep.
As for the new minelab 11" coil....I would give it a little time before you decide on it. I think it will be a good coil..but only a little time will tell. There are a few experienced hunters who already have...or will have that coil and they will be posting on it. It might turn out to be a great coil so I would give it a few weeks and see how the reports come in. Same as with the sef coil I'm trying. It should be a winner too...so just check out posts as they come in.
Now that I'm done rambling

...the coils I can recommend from my own personal experience that i have already had good success with...the Minelab 1050 coil...the excelerator 10 x 14 coil...and the excelerator 6" coil.
Also please remember all I have said is my own personal experiences and tests. Each person has their own settings they prefer and different settings...coils...and sites will obviously give different results.