I own the EMU 0404 USB and can highly suggest it. Definitely the best for the price. Quality of pres and conversion far surpasses the Presonus firebox.
With that said the ECHO is also a great unit.
I'd suggest picking up a Shure SM57 and the EMU 0404 usb interface.
I tried the M3 and wasn't impressed at all on any app I put up against it. This was a SDC shootout I did myself with a lot of other mics including Shure KSM137, KSM141, KSM109, ATM450, Rode M3, Sterling Audio ST31, Rode NT5, SM81, and AT4041.
Mic cables were Mogami Gold Studio and mic preamp was a Trident S20. My monitoring for the test was my Beyer DT770 headphones and then a pair of JBL LSR 4328. Room was acoustically treated with traps, broadband, and diffusers. Hardwood floors etc.
Testing was done using a couple acoustic guitars Gibson SJ200, Taylor GS-K I believe (it had a solid spruce top with flamed koa back and sides), Martin D-35, and my Epiphone Masterbilt AJ500R.
I also tried miking up drums and cymbals from overhead and as a hat and ride spot mic. I used my set of K Custom Hybrid cymbals and a set of A Custom Rezo cymbals. I used a DW Collectors Series (maple) 5 piece kit (18x23 kick, 7x10, 8x12, 11x14 with legs, and 13x16 with legs) with a 6x13" EDGE snare.
Judging by how the M3 reacted to those sources (one's I was very familiar with) I can safely say I wouldn't choose an M3 over an SM57 or any of my other favorite instrument mics on a guitar cab or for an acoustic guitar.
heil's
pr-30 and
pr-20 ut are excellent alternatives to the industry standard MD421 and SM57 in my opinion. the BLUE Ball is also a great alternative and is surprisingly affordable now, you just have to talk to your BLUE dealer and have them order you one.
In any event the mics I listed will be able to last with you forever and will stand the test of time I just can't say the M3 will be a lasting hit like an SM57, MD421 or like the Heil dynamics will be.