The delhezi and ornatipinnis are the smallest at around 6". The palmas palmas (thanks to Infblue for identifying it) is the biggest (length and girth)at about 8" long. If I recall correctly, they were all about the same price (the ornate was the cheapest, rest about the same).
The "final" tank for them will be a 72x24x30 (210 GA) with red quartz sand, a waterfall (tank filled maybe only 22") w/ a DIY styrofoam/concrete facade background. It's going to be a lot of work and time, but it should look really cool when complete.