It is not worth all the RR spells to upgrade so delete it for space. (My opinion)
The KP can easily be bought daily. I buy 3 a day and so long as you keep the cost below 5% of the full main hall you cannot go wrong.
Also a few Carting Libraries preform much better as do the Monument of AW if KP is all you need.
i upgraded and i'm keeping mine. 6400 people, 8700 culture, + the kp, + mana, + seeds, + coins, seems like a lot for a set that's probably 28 squares. 2 of my homes take up 30 squares and give me just 7000 people.
It has one of the few event buildings that gives a decent amount of seeds - the Yeti Santa Factory. Mana-producing event buildings are common but good seeds buildings are not.
Remember you don't have to upgrade all the buildings - the sets work fine if the buildings are at different levels. So if there is one that you particularly want the rewards from you could upgrade just that one to get the higher output from it.