I totally agree to get the diamond that sings to you!!
I was at the Jeweller's the other day just nosing around, and was shown 2 triple Excellent Diamonds (i.e. Excellent in Cut, Colour and Symmetry) of the EXACT Carat weight except one was an EVS1 and the other an FVS2.
The Jeweller asked my DH and I to pick the one that was more sparkly and I chose the FVS2!


The DH was equally lousy...He couldn't differentiate the 2 at all!
That being said, I have a 1.5Ct Diamond that I bought for myself and has been nothing but proud of its "Bling" for years. I was recently given a Ring that looked as if it had a larger carat weight but was so dull I didn't even think it was a diamond initially! (It was a gift so I felt it was rude to ask....

ush

It turned out to be a diamond that was
ALSO 1.5Carat but cut to look larger than it really is. Even after a good polish, it didn't even sparkle as well as the two 0.2Cts the jeweller randomly chose for me by its side when I reset it.
Since I am always on a budget, and 4 Cts is by no means a small sum of money, I'd suggest doing some comparison too (Unless you already KNOW you love it of course!

).
Afterall, you won't be able to detect the Clarity with the naked eye too, so you can always trade down the VS1 clarity to obtain a better colour. Similarly, you can also get a
slightly smaller diamond, maybe 4.03 or 4.04 but with a better symmetery so the facets in the diamond reflects light better and it sparkles more, but no one can tell the difference of the carat weight visually...
Of course it is not like you will be carrying your diamond around only to compare it with other diamonds, but when you do sit down for coffee with your girlfriends and they "Oooh and Ahhh..." over your Headlights of a ring, wouldn't it be kinda nice if there is no probability for one of them to ask you..."Hey, is it the lights or does your rock look kinda yellow when compared to mine?"
Especially since 4 Cts has a larger surface area....
Just my $0.02.