25K! For an HIX?! What's going on in this town? HIXs are usually 10K, What gives here? I just paid 10K a night for an HI in Warsaw where the going rate was E180! If that's the real number of PC points needed, pay the money. 25K will get you a CP in London, England that goes for £150+.
As for a conversion rate with SPG points, 3/4 to 1 is a very rough measure but that would mean a category 4 or 5 SPG property for an HIX, again a pretty lousy trade. Pay the money at this property and forget using points from any program.