If I remember correctly, IMP Skeet is a couple thousands tighter than Improved cylinder, so between an IC and a Mod.
All standard target or hunting shells are around 1200 fps, whether it be 10, 12, 16, 20, 28 or .410. You can buy faster go boom shells that will get you into the 1500fps, but they tend to blow out patterns and your shoulder, generally having softer shot unless you go with copper or nickel plating, but for doves this is not necessary. The best thing you can do is buy decent target load whether it's Win. AA, Remington Premiers, or Federal Top Gun target loads. Fiochi makes some decent shells also but are not as common. I usually reload my own to imitate a target load for hunting purposes.