One thing I strongly suggest you satisfy yourself about before making a commitment is to understand exactly what the differences are among these instruments. The Schiller, Wessex, and Mack Brass are all Jin Bao and fundamentally the SAME INSTRUMENT. I don't know about the Packer. There may be some differences (such as an extra water key, inclusion of a particular mouthpiece, etc.), but you have to be aware of what the real differences are because there are some price differences here. Beware also of shipping costs and any import duties if you buy from anywhere abroad.
Also note that Tom McGrady is still offering his 100% refund satisfaction guarantee (that includes shipping costs both ways) if you're not happy with the instrument: http://www.mackbrass.com/MACK-EU1150_Comp.php.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)