Your printer will operate properly as long as you keep the bottles at the same level as the printer.  The padding in the cartridges creates a nice pressure buffer so that the printer is able to operate with various ink levels in the bottles.  If you raise the bottles up to a higher level, you run a risk of ink pooling on the paper.  Keeping the ink way below the print head (by elevating the printer) does not influence the quality of the print, but may require a clean cycle after prolonged sitting since the ink may be pulled out of the nozzles slightly due to the negative pressure.
In normal operation with the bottles sitting next to the printer, you will experience the same great print quality no matter what the level of ink in the reservoir bottles.  In fact the print quality should be equal to what you get with a fresh, full cartridge all the time.  (Normal cartridges tend to degrade in quality as the ink level drops)