I have not used this exact setup but have run very similar systems. Basically identical but with a different pump.
If you're looking to purchase the minimum pump needed to power your system, this will also be determined by the flow-rate of your nozzle. I assume you already know this but thought I should point it out just in case.
More importantly, there is no problem that I know of from running less nozzles off of a pump capable of handling more. And you always want a bit more power from your pump to handle slight variation in your system. Water quality, voltage variations, and droop in your lines can all affect flow rates.
If the Rio 2500 can power multiple nozzles I'd say it's a great buy at $40. I've certainly used more expensive pumps for just a few mist-heads.
I hope this helps.