Is it true that multiples of 1000 DRK increase the chance of masternode election for one node?
No, not true. If you had multiples of 1000 DRK, it's far better to run multiple nodes.
In RC3 Multiple entry Masternodes are coming (Evan said it in IRC) so you'll be able to put 4000 DRK (aka close to 60 000$) on a 4x payout Masternode if you feel like it and get an increased chance of payout instead of having to set up multiple nodes which could clutter up the network.
Cool.