Acorn Hill Farm in VA has lots of young stock from multiple stallions (including Pallas Digion, sire of Sharon Hunt's Tankers Town and a couple other Advanced/CCI*** horses) in various levels of training. I got my young horse there (she's by Carrig View, who also evented through Advanced) and I'm seriously in love. If I was going to get another young horse, that would be the first place I'd look.
Regardless of your budget, he has the ability to find the most amazing young athletes with raw talent and great minds. I have purchased numerous horses between 3-5 years of age from him and each has far exceeded our expectations. As a side note, Ryan is currently helping Zara Phillips find some young eventing talent and he is well regarded among the British eventing community. Two of my more recent purchases from Ryan successfully went from Novice (as 5 year olds) to the 2* level in less than one year with a reserve champion and 3rd place finish at the 5yo YEH championships last Fall. A new 3 yo just arrived from him and I'm ecstatic about this little guy as well. When Ryan rings to tell me about a fabulous young horse, I wire the money instantly....sight unseen. That's how much I trust him and value his insight and keen eye! Even if you have to adjust your budget to compensate for the cost of importing, I can assure you that you won't be disappointed!