You probably don't NEED 25K chips unless you are planning 4 table 20K tournaments. Then the entire barrel of 25K chips still represents about 60% of the chips in play. I don't think you can accomodate that in 1000 chips. Maybe with 1200.
With 900 chips, I think you have a pretty straight forward 30 player set.
30 * 8/8/4/7 (of T25/100/500/1000 for a T10K starting stack) plus one extra T1000 chip for color ups.
This gives you a set of 240/240/120/240 for 840 chips. If you do 60 * T5K chips that brings to to 900 and enables you to accomodate one T10K rebuy per player, or expand the starting stack to T20K on occasion.
So on net, this would require an add of 90 * T25, 90 * T100, 105 * T1000 from your current stated totals.
If you were to try for a 40 player set, you would be looking at 1200 chips like this.
40 * 8/8/4/7 (of T25/100/500/1000 for a T10K starting stack) plus one extra T1000 chip for color ups.
Putting you at a set of 320/320/160/320 for 1120 chips, with 60 T5000 chips and 20 T25000 chips to make 1200.
That would mean on net you need 170 * T25, 170 * T100, 35 * T500, 205 * T1000, and 20 * T25000.
Alternatively, you could forgo the 40 extra T1000 chips for color ups and use 40 extra T5000 instead.
This would give you a set of 320/320/160/280, with 100 T5000 chips and 20 T25000 chips.
On net this is 170 * T25, 170 * T100, 35 * T500, 165 * T1000, 40 * T5000 and 20 * T25000.
This alternative has more flexibility for T20K starting stacks instead of T10K.