Mars is junk. People who are supporting MARS either don't realize their light is less efficient and more expensive than an average (less expensive) HPS setup or are trying to justifying to themselves how they spent all that money on JUNK. There is zero benifit to a Mars unit unless your comparing it to an incandescent light... and NOBODY is growing with incandescent bulbs.
We really need to know what your HID setup is (make/wattage/ cool tube?) to be able to suggest a setup that would equal or outproduce what you have.
For your budget of $300 for 9sq/ft buying a more efficient HPS is the best bang for your buck 9 times out of 10- quality DIY LEDs would probably be over budget and are difficult to efficiently vent waste heat outside your tent.
What has been discussed multiple times - any Watt put into a tent in any form (waste heat, photons, imaginary MARS numbers) is going to be heat eventually - so you have to manage it. The LED s would be a benifit for you when running at higher efficiency ONLY because watts from the wall can be reduced while maintaining your PAR levels and this is almost exponentially(not really exponentially - but awful nonetheless) expensive once you start moving above 50%+ efficiency.
So it's go big or go home with LEDs. That's the honest truth...for the next couple years...
9 out of 10 times - so enlighten us further on your current setup so we can get you in the 1 time out of 10 group