i am thinking that using an online print house is easier and the cost is about the same with all things considered.
Based on some recent research on my part to decide whether I upgrade my Epson R800, or rely on services for large-format prints:
Assuming a good, calibrated monitor and optimal workflow, on-line printers can make good to excellent prints from most colour files, on a limited choice of papers. For fine-art papers, and for subtle images, a good inkjet (eg. Epson 2880/3880) gives one the most control and IMO, optimal results. You can also work with "pro-quality" on-line services for the fine-art/subtle pics, but these come at a premium price. B&W is a different story. Typical C-prints in B&W are "just OK" IMO. Epson's ABW, and pro-quality services (either inkjet or lightjet) do much better B&W; expect premium prices for the on-line pro services. I don't have any personal experience with MPIX's "true" B&W, but it is an economical alternative, if it works well.
EPSON Pro 3880 ink/paper costs (very approximate):
17 x 22, Epson Premium Lustre: $6.50
17 x 22, Hahnemuhle Photo Rag: $11.00
MPIX
16 x 20 C-print: $18. ($20 Metallic)
16 x 20 "True B&W": $20
Giclee (inkjet) from local providers
16 x 20 Lustre: $18 to $55
16 x 20 Hahnemuhle Photo Rag: $42 to $90
Dalmation Custom B&W:
16 x 20 K7 Piezography on fine-art paper: $104
16 x 20 Lightjet on true B&W fibre: $118.