The majority of good coolers require a backplate which would require mobo removal if your case doesn't have a cpu cut-out.
More info like your ram height and case width would be very helpful.
Anyways here's some good units for mild-mid oc's that don't cost alot.
COOLER MASTER Hyper 212 Plus - usually can be found for $20
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065
XIGMATEK Intel Core i7 compatible Dark Knight-S1283V
http://www.newegg.com/Product/Product.aspx?Item=N82E16835233029
CORSAIR CAFA70 - includes 2 fans
http://www.newegg.com/Product/Product.aspx?Item=N82E16835181011
ZALMAN CNPS10X Performa - The CNPS10X line is preferable because the fans are user replaceable.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835118059