As one who is neither Catholic nor Evangelical, or maybe one who is Both/And, these comments on sola scriptura are worth the read. (You'll need to scroll down the link a bit.)
Apart from the intriguing account of the conversion of a prominent Evangelical, Fr. Neuhaus points out that it was St. Athanasius in 367 A.D. who "was the first to name the twenty-seven books of the New Testament as canonical."
In other words, the Scriptures are never alone. They are preached, heard and prayed in the midst of God's people in the Church. They are recognized as inspired and authoritative by the Church for her guidance in a common tradition by the Holy Spirit since they are revelation of God Himself in Jesus Christ.