Hi Pat, in each case...you'll be heavy on T500 (if you go T25 or T100 breakdown).
So I would go for T500 breakdown and do 10/10/6 for 100BB (2 tables) or 1 table with rebuys & color up chips.
18 players
18 x 10 (T500) - 180 chip (20 left)
18 x 10 (T1K) - 180 chips (20 left)
18 x 6 (T5K) - 108 chips (12 left)
You only have 80K in color up chips for 90K in purple (18 players)..besides that, everything should work out.
2 more brown chips and you are set.