The reason he says the stripe kit is not needed, for the most part, is they had to pull them and are supposedly reworking them. Not available last I checked and they were to be priced out at around $500.00!!!
From what I've seen they stripe ok without a kit. But given the option, if they aren't too crazy expensive and function well (ie. out of the way, don't high center the mower, don't require a lot of maintenance) I would buy one. Hands down take the striping to a hole different level. I had the original version on a 60" standard deck which was virtually a thick mud flap on the rear frame between the rear wheels that was adjusted 2" from the ground. Did pretty good, especially 11 years ago and it helped brake up the clippings a little. The only down side was if you were mowing nasty places like ditches with a front caster hanging in the air etc. it would some times high center,leaving one or both rear wheels spinning, even though it folded a little. You'd have to get off the machine and pull the front end to the right or left till it was off the striper. Doesn't happen often once you use it you know what to watch for and how to handle it.
The later version of the stripe kit is similar to Exmark. It looks like a piece of heavy duty, large, drive shaft material from a truck made into a roller that fit on the back of the deck and is adjusted again roughly two inches lower than your cutting height. It worked much better. Bearings wore out about every other season and were expensive $100ish). But it moved with the deck and you stop and start the striping by raising and lowering the deck which was handy. It also helped with scalping.
The new model is more like the early idea. When they built the new machine they didn't allow enough room for the roller to fit between the deck and rear wheels. This is the theme a lot of manufactures are going with. I believe the closer the main wheels of the machine are to the deck the better the deck follows the contour of the ground, helping in both QOC and scalping. So the new unit will hang off the rear. Question is if we will need to raise and lower it manually, if it can be left down all the time, if you have to get off the machine to do it etc.
Flex forks are a love hate thing. Def. helps the ride. Down side is until you get use to the mower you will scalp and terrace more because the deck is moving up and down with the front of the mower. Stop too fast, turn too fast,
Hit too big a bump and you will see it in the lawn. It's easy to do on a fast mower. Also side hilling, the lower edge will dip more causing terracing where the joining stripes don't match up in height. This is worse on the bigger decks (66" and 72") You learn to float the deck with your foot pedal in any or all these situations, when needed, which lessens this a lot and gives you one strong leg. The only other negative is if you buy a bagger. They weigh quite a bit and will lower your deck cutting height by about 1.5". Which requires you to add air to tires and raise the deck height by eye and not the gauge. This being said I'll have another set on my next Hustler if I buy one.
Do the suspension seat for sure. Don't even question it. Even with the suspension seat it's not the smoothest out there. The earlier XR7 decked machines had an $200 optional flex or rocker platform that could be added under the suspension seat which I've never tried but have heard it was wonderful. The new machine will not accommodate one due to the huge hydro reservoir. In my mind they need to do what some of their competitors have done and add a isolated platform where the foot tray, steering levers, and seat tray are mounted in rubber in addition to the suspension seat. Husqvarna and Gravely have gone to this. Scag Cheetah has their own version witch looks comfortable but I've read threads about center of gravity being higher and the movement interfering with operation of the machines controls. Gravely also took it a step further and has an air adjustable air ride seat in addition to their isolated platform. IMO this would the correct direction to go instead of flex forks.
Some other things you may consider is pneumatic tires on the front. As of this year most commercial Zs have gone with flat free tires which ride hard and get sloppy on the rim, but they never go flat. I've had only two flats in 2000 hrs machine time on a front wheel, so to me it's not an issue. The ride is twice as good the the ribbed Carlisle pneumatics.
I'd get the trailer hitch. Not a big item but comes in handy.