I'm strongly opposed to these proposed new rules, and have stated my reasons numerous times in this thread and previously. But many Nascar fans as well as almost all of the writers and commentators are excited about "the All Star package." You are dreaming if you think the vast majority of fans agree with you and me on what constitutes good racing. I for one feel
@StandOnIt deserves respect as a passionate fan of Nascar and other racing. Although I disagree with him on this one issue, both sides are opinions.
I believe your numbers are wrong, and it probably comes from confusing semantics. All Xfinity engines are artificially restricted in their air intake tract. At Daytona and Talladega, the restriction is via plate and results in about 450 HP. At all other tracks, the restriction is via tapered spacer for about 650 HP. The confusion is that these tapered spacer motors are often referred to as "unrestricted" although that is a misnomer. (And these cars have more drag and more downforce than Cup cars at all tracks, so extrapolating speed is questionable.)
Cup motors were free of artificial intake restrictions at 32 races up through 2014. They made about 850 HP, some say 900. For 2015, the Cup tapered spacer was mandated, which reduced HP to about 725, but that is still called "unrestricted" by many. At Daytona and Talladega, the plates yield around 420 HP. The new proposal for the so-called "NA18D" package is 550 HP. This is slightly more power than Daytona, but less than Xfinity.