XT8 Telescope highest magnification?

I own an Orion Skyquest XT8 Clic Dobsonian telescope. The provided 25mm Sirius Plossl eyepiece (48x) is good, but im looking to bring the images closer and up the magnification. I know Orion says the highest useful magnification is around 300x, but thats only at near perfect viewing conditions. i was trying to find a more realistic estimate of how much is too much, along with some recommendations of eyepieces. Please, dont recommend any eyepiece more than $150. Too broke to touch TeleVue Naglers.