The most popular em solutions out there are: accesport, utec, ecutek, and open source. Open source tools is the cheapest option, hands down. All you need is the $85 cable and a laptop. It seems like you're avoiding em, but for $85, you really have no excuse but to get it now. It's one of the best bang-for-the-buck mods out there. I'll even give you step-by-step instructions:
1. Go to www.tactrix.com
and purchase the cable that says "OpenPort for Subaru Drive-by-wire vehicles."
2. Visit www.openecu.org
, click "downloads" on the left, and download ecuflash.
3. Read the enginuity faq: http://www.enginuity.org/about444.html
. Scroll down to where it says "Q: How exactly do I download and flash my rom image?" It will tell you how to use ecuflash and download your rom image, as well as flash your ecu later on. (in step 7)
4. IMPORTANT: save your stock rom image in at least 3 places!
5. Visit www.plasmatize.com
6. Go to the home page, scroll down and click on the link that says "2006+ Modified." You'll see stage one and stage two maps that are set and ready to go already for your car. The maps are for 06 cars, but I don't believe there were any significant changes between years, so you should be fine using that. Stage 1 is for stock cars, and stage 2 is for those that have a turboback exhaust. Since you are stock (for now) download the stage 1 map.
7. Load the map with ecuflash.
8. Following the directions on the same section of the enginuity faq, reflash your ecu.
Other things you should know about open source tools:
1. It's called open source because it is being developed by enthusiasts for FREE. That's why all you need to purchase is the cable, and all the software is free.
2. There are a number of different programs you can use. There are programs that:
a. Read/write roms on the ecu. ECUFLASH
b. Edit roms. ENGINUITY
c. Datalog. ECUEXPLORER
You only really need type 1, or ecuflash. If you want to tune your car yourself, you can do so with enginuity (there are other options out there of course, but enginuity is amongst the most popular). Just be very careful, because if you don't know what you are doing, or you could seriouosly damage your car (and yourself).
3. Learn how to datalog with ecuexplorer. It's quite easy, and will help you troubleshoot your car and make sure that it is running well before/after mods.
4. Read, read, read! Learn as much as you can from this, and other subaru websites. Make sure you read the entire enginuity faq that I mentioned earlier. There is also a great engine management faq on this website. Read that.
5. You don't need/want a boost controller. Engine management wil manage boost for you.
6. Try looking for a local tuner that uses open source tools. Even if the closest one is hours away, it will be well worth the drive.
As far as the fmic, you won't benefit from it much unless you have a pretty big turbo. Take a look at the ssautochrome top mount intercooler on ebay instead if you're looking towards that direction. For $183 shipped it cannot be beat, and it has been proven to perform well.
As I said earlier, the intake is not worth it. The stock box works VERY well as is. Save that money and buy the tactrix cable instead.
Your year doesn't like to be modded much w/o em. With the 02/03 wrx, you could get away with quite a bit of mods w/o engine management, but the same cannot be said about your year. You may experience erratic boost spikes and other things if you are not careful. Most mods that are worth doing will require engine management. There is no way around that. Good thing I already solved that issue for you!