I own a impact-x, upgraded with a powerplenum, which make it 95% a mk2. It is a nice gun, but might be a litle challenging to tune with light weight pellets. Tried to tune mine for 8 grains, but went back to 10 grain, as it seem a lilte hard to "tame" . Do not think the big powerplenum is nescesarry for .177, as that caliber use litle air. Do not know how the M3 is, but since you do not plan to shoot slugs, I believe some of features on the impact is not needed if you plan to use it for .177 only. It has bigger valve, and plenum, than most .177 gun, and probably more suited for higher power, or bigger caliber setups. In my opinion the impact also needs some after market accesory, if you plan to use it for bench shooting. I added a bagrider on mine, as it is not suited for resting on a bag in stock form. Also a extended rail, or bottle rail adapter is preferable, if you plan to use a bipod.
You did mention the uragan. I do not know about that gun, but I have a AGT vulcan 2 tactical which is made by the same manufacturer. When I only adjusted the hammer spring tension down a litle, it is as accurate as my impact, even at 60 yards. The regpressure on it seemed to be setup perfect for a 10 grain JSB pellet, from factory. It will probably not be as powerfull as the impact, but it is in my opinion not needed for pellets. It is also easy to shoot on a bench, as it is a litle longer than the most bullpups. It was a litle loud for my liking with the stock shroud, so I removed it, and got an adapter, and added a moderator directly to the barrel, which made it quiet, and not any longer. My experiance with AGT has been positive, and since you do not want a compact gun, a tactical vulcan might be a good option. It is not as long as a rifle, but feels like one when handling it. It doeas not have a bottle, but the tube is in my opinion big enough for .177 and gives plenty of shots.
I can not speak of the daystates as I do not own one, but I must admit if money is no issue, the deltawolf seems tempting to me personally. It seems to have all the tunability, and as far as I know are setup good from factory.
If you are not a tuner, it is important the gun is setup good from factory/dealer, as othervise you might not be satisfied when you get the gun. Some guns might need some accesories, like another moderator/adapter, or a rail, if you plan to use it for bench. And some might need adjustements on the trigger before you get it where you like it.