Honestly, the only necessary upgrade needed is a clamping feedneck. The stock one doesn't accommodate the larger loaders (Halo) even after the 2 large O-rings have been removed. ANY clamping feedneck is fine, they are all adjustable. Brand is up to your preference. Once I saved some money, the second upgrade was the trigger. The stock one sways side to side. The shape is W, I prefer an S shape, easier for higher rates of fire. After that upgrade, I replaced the traditional duckbill ASA with a 1.5" dropforward w/ on & off. Any other upgrades can come along, this sport is expensive as it is.
Stock Parts (barrel, trigger, feedneck and ASA)
-you can usually find this at local shops for about $225. Not bad at all considering electro-pneumatic markers were an average of $900 back in the day.
-clean up is a cinch with the B.O.B (bolt-out-back) design. 1 allen key is all that is needed to remove the bolt.
-with the popularity of the SP Ion XE continually growing, many after-market upgrades are available. Heck, you could build a complete custom Ion from the ground up, that's how much stuff there is for it.
-with the new spool valve tech, the guts in the marker are simplified. It is efficient operating at an average psi of 180-190. For those who enjoy doing their own repairs, there is nothing intimidating inside. Simple hoses and fittings. There are MANY tutorials on how to make any adjustments to better suit you.
But to be fair.....
If Smart Parts were to include all of those upgrades, then the price of the Ion wouldn't be $225!
I've played paintball for many years. I've seen markers come and go. This is definitely one that will stay. It is affordable, efficient, durable and VERY customizable. There is no need to drop $700 right off the bat to get something sweet. Only a minor upgrade (feedneck) is needed when first purchased. Other parts can be upgraded later.
If you are on a budget but want a high end electro marker, then this is a perfect choice for you. I'm rating it a STRONG 9 because the body could've used a little bit more styling.