No personal interaction with them, but Sign X is a 4-star rated company (out of 5 stars) on another site with the latest rating dated in September this year.
Google search of Signature Xcel shows this;
Signature Xcel / Sign X
Website: (http://www.signaturexcel.com/)
Notary public in Phoenix, Arizona
Service options: Online appointments
Located in: The Courtyard
Floor 2, 7330 N 16th St Suite A220, Phoenix, AZ 85020
Phone: (480) 530-7446