Welcome to the site Haretrigger You'll find all info you need here shortly. Patience is a virtue I'm not an expert in the gun dept. but there are lots of well informed people here. What are you planning to hunt with a more powerful gun?
325wsm is an OK cartridge, although personally I'd stay away as a general purpose hunting cartridge, especially if I were not a reloader. It's basically a 8mm bullet on the 300wsm case (note that they didn't call it 8mmWSM but yet linked it to the 338 win mag in the ads... ).
The 300wsm is underpowered compared to the full length 300 win mag (suprising but true. factory comparable loads but the 300wsm about 100fps or more below the 300 win mag). Ammo will be harder to find and costly in some instances.
I would look at either the 7mm remington magnum or 300 winchester magnum. Both out perform 270 and 30-06. 270wsm is also a good cartridge (delivers solid performance gains over the 270 win), although you are limited to a max bullet weight of 150gr, which is probably a bit light for some of the game you list.
Given The animals you are looking at hunting primarily(elk, moose) and wanting a more powerful cartridge, I'd go for the 338 win mag. It is a beautiful round for larger framed animals and the ammo is wide spread and cheap compared to some of the newer magnums.
There can be too much of a good thing with antler rattling.
I like to hit the horns together for a good 30- to 40-second rattling sequence and then hang them up and resist the urge to hit them again.
This works to the hunter's advantage, because if a buck has heard it, he may have been 300 or 400 yards away and he comes in and he's not exactly sure where it came from.
When finally is time to rattle again throw a slight change-up into the routine.
The second time, don't rattle as loud...