Low 50s rwhp is easily possible without spending too much money - PCV, stage 1-3 air filters, pipes and a bit of dyno time. To get any more than that (and to get close to 690 power) you're going to have to invest a lot of time, money and effort - big bore, longer stroke, heads, cams etc. All of which will ruin your low to mid-range power on the XT motor. However, it will go like sh!t off a stick if you give it some revs!

__________________