I feel like I'm writing a book! I would rate the 5400 as "OK". It will probably no-till as good as what you have. Seed spacing, not so good. There were several in the area at one time, but I don't think I've seen one in the field for a couple years. I love the openers, like the big seed box. Hated the OEM meters. Fluted meters are a controlled spill.
The 5400 has some problems. The early ones had this bad habit of breaking in two. The hitch had a weak area and the u-bolts mounting the wing wheels were too small. I suspect any you find have had those problems addressed by now. Seed spacing is atrocious. The rubber tubes either bounce seed around between the meter and the opener messing up spacing, or they gooseneck and cause the seed to bunch. That was our biggest disappointment with the 5400 and we never did get it resolved. We replaced the rubber hoses with PVC pipes that slipped inside each other and helped some. But if they stuck it broke the meter housing.
Another problem with the 5400 is negative tongue weight. You really need an articulated tractor or at least a front wheel assist pulling it, because when it is full as you raise it out of the ground it takes weight off the drawbar. I was almost stuck on dry ground one time. Raised a nearly full planter to turn on some very sandy soil and spun out because the planter pulled the weight off the rear tires. Neighbor said if he hadn't seen me do it he would not have believed it. That also means when you hit a soft spot and raise the planter all you do is mash the transport wheels in the ground. The most stuck we ever had a tractor in the last 20 years was a 7120 Magnum pulling a 30 foot 5400. We literally broke every chain on the farm getting it out.
We had a problem with the transport wheels pulling bolts out of the hubs. We eventually got long wheel bolts and put red Loctite on nuts on the back side of the hub. I know whoever bought that planter has spoken ill of me by now.
The SI belt meters are a great improvement IF you understand their one problem: They CANNOT handle big seed. Since so much of our seed beans are large seeded varieties these days that is a major issue. And seed count does not tell the story. You need to run a sample though a grading screen and see what will feed and what won't. I was infamous at Beck's for a while for rejecting 2 tri-axle loads of bulk beans because even though the seed count was OK, there were too many big beans that would not feed through my sample screen
We've had a lot of different planters over the last 40 years. I've tried several different bean planters.15 foot 510 IH drill, 24 and 30 ft 8" spacing Great Plains drills, 20 ft 15" spacing planter made from 800 modules with Tye drill openers (I think it was leftovers from someone's project. Actually worked great, just not wide enough), 30 ft 15" spacing 5400 with SI belt meters, and 30 ft Kinze rear fold with 7000 units on 15" rows with brush meters. Current bean planter is a 30 foot 23 row using 3 - 800 modules on 15" spacing.
I told you all that to tell you this: I've used a lot of bean planters and have been the most disappointed by the 5400 Soybean Special.
