Need Help with the Monster Party

[TabletopGamer]

Ok so we are gonna have a monster party.

One is a Pixie (http://www.d20pfsrd.com/bestiary/monster-listings/fey/pixie)

One is a Lythic (http://www.d20pfsrd.com/bestiary/monster-listings/outsiders/elemental/lythic)

One is an unknown yet probably an Advance Doppelganger (http://www.d20pfsrd.com/bestiary/monster-listings/monstrous-humanoids/doppelganger)

I am playing a Leprechaun
But I am not sure if I should use this one (http://www.d20pfsrd.com/bestiary/monster-listings/fey/leprechaun)which is Cr 2 or the CR 4 3rd Party one (http://www.d20pfsrd.com/bestiary/monster-listings/fey/leprechaun-TOHC)or combine the two.

Use the CR 2 as a base (Its the official one)
But add on a +2 Int and make the polymorph any object (objects only, DC 21) match the 1/day of the Major Creation. And have the permanent image (visual and auditory only, DC 19) to the 3/day of the base.

With the changes would this make it a CR 4?

[ngilop]

add on some class levels would be the easist thing to do.

playing as th CR2 leprechaun nets you 2 (or 3-cuz im not sure if PF does teh class level-1+CR thing) levels in X class.

[Metahuman1]

Personally, I'd take that CR 2 version and just start applying Caster levels. Boosts to all 3 mental stats + Dex + Con? Yes Please!

[TabletopGamer]

Well the reason we are trying to balance our Crs is that if all are CR 4 or close to it then we can ignore CRs totally and just add class levels. Adding a +2 CR to all monsters or so might be needed but not for PCs

[Metahuman1]

In that case, I'd find a template and drop it on the CR 2 version to get it up to CR 4 and then just go, "Ok, were all CR 4 critters, let's add class levels and get going."

I'd also pick a caster class and a template or two that add to Your primary casting stat and your Con, maybe then your Dex.

[TabletopGamer]

The second 3rd party one is a 4 CR race so I was curious if I could just increase the CR of the official. The polymorph any object is sure to have an effect on the CR of a race.

So would this grant the +2 needed? If I needed to add say Advanced to a +1 increase for the 4 Cr needed?

[TabletopGamer]

All I really need to know is if:
Polymorph Any Object (Objects Only; DC 21) as a once a day, Permanent Image (Visual and Audio Only; DC 19) three times a day would make the character a CR 4? Would it make it a CR 3?
Polymorphing is a very strong power already and the SR 27 can be very nice overall too

Maybe if I tagged the Advanced Template on to the Leprechaun with those spells?