The KG 2.2 or 2.5 were designed as centers for the KG line. Being a small "bookshelf" size, they were popular in their day, and therefore are fairly often available on the auction sites. Should be able to get one for $100 or less. I would not worry about putting a KG 2.2, 3.2, or 4.2 in with your 4.5s, but other opinions may differ.