ALso, the NX doesn't come standard with the bells and whistles that the DK did and it is a lighter tractor (weight). E.G. of bells and whistles, sway bars with the telescopic rears, tool box, extra rear port, rubber mat for floor - those are all add ons that used to come standard. THey may display them with the mat on the operator area, but the dealer ordered it and it increased the cost. to lift as much as you said, you will have to move to the rx series and that is 60+ hp. I've been comparing and pricing since my gears went on my DK. I wasn't a happy camper when I saw the new ones with the tier 4 engines. I'm leaning towards and RX or going Red (they still have the heavy rears on them like the DK's did). I do a bit of loader work with my tractor so weight does matter to me, although the average owner wants a lighter tractor and my guy is telling me all the major players are moving in that direction as well as lowering the entry price points by manipulating the standard equipment. The NX is prettier, and the loader arms are more curved but I see they didn't fix the loader interfering with the lights.
Hmm, PA hayseed, my experience differs on some of these points. I shopped pretty hard when I bought my NX4510HST Cab early last year. If you compare the two tractors the OP cites using Kioti's online comparison tool, the open-station NX4510HST is actually 65 lbs heavier than the open-station DK45SE HST. If both are cabbed, the DK45SE HST is heavier by 51 lbs. The DK lifts 2493 lbs at the 3pt hitch; the NX lifts 3177 lbs.
http://www.kioti.com/wp-content/themes/kioti-main/compareModels.php?models=176,5055,5074 If nominal lift of 3200 lbs is what you want, you don't need to go to the larger-framed, geared-only RX series (although the RX is very nice). Curious if someone has said these specs aren't accurate.
My NX came standard last year with telescoping lower link arms and floor mats. Haven't seen or heard of a dealer stocking or even ordering NXs without them. Agree that the rear remotes and a toolbox are optional in the NX, while the DK comes standard with a toolbox and one set of rear remotes. (About $250/set for the remotes for the NX if dealer installs, subject to negotiation). With cab tractors, neither the DK or the NX offers a toolbox, but small tools stow well behind the seat in a couple of 15" soft canvas tool bags from Harbor Freight. In a DK cab tractor, a factory radio-CD player is standard; optional in the NX, but easy to add an aftermarket with more features if you wish (e.g. NOAA weather radio frequencies, Bluetooth, USB ports), without paying for the factory radio as well.
Other nice touches on the NX, as well, in addition to the electronic HST. There are a few new DK45SE HSTs still out there, though hard to find as Tony says. (I see James K0ua has just started a thread on that). Suggest the OP kick the tires on both series to get a better handle on the bells and whistles aspect. Regarding the new 3 cyl. Final Tier 4 in the NX, I've been very pleased with mine. Very smooth and quiet, and starts, literally, instantly in the relatively cold weather we've had here in No. VA this past year (10 - 15 F). I only have 100 hrs on it, but they are hard hours, mostly grading work with box blade and loader in low or medium range at full throttle, and rear-blade snow plowing. The emission system has only regenerated once in that entire time, so the work load seems to agree with it. BTW, there seems to be some disagreement on TBN on the issue, but I believe that all DK series sold new in the last few years are technically Interim Tier 4, rather than Tier 3.