Like you, I have a 99 Outback. I bought it back in 06, with 148K on the odometer. I now have 256K on the odometer, and she still runs strong. I put on KYB struts at around 160K miles. I did not replace the springs, and have not regretted it. The KYBs run great, and last a long time. The probable original springs still seem good as new.
99 Outbacks have an inherent problem with the transmission, in that it will develop a delayed forward engagement from park. The problem is that Subaru went to a revised tranny in 99, and a valve unit fails to operate properly. It can be corrected with a tranny additive. If your car has, or develops this problem, do a google search for "Subaru, delayed tranny forward engagement." I started the topic back in 2008, and it has helped many Subarus.