SCUBA and AMBO surveys at ~1mm have revealed the presence of a rich class of high-redshift powerful starbursts, ultra-luminous in the far-infrared ("submillimeter galaxies", SMGs). They are probably the progenitors of present day massive elliptical galaxies, caught at the epoch of one of their most important merger events. This field is now revolutionized by the wide-field surveys carried out by space observatories: 1) Spitzer and Herschel have increased the area observed by two and soon three orders of magnitude, respectively; 2) the submm bands of Herschel provide direct information on the far-infrared luminosity and the star formation rate of such galaxies. I will focus my talk on the results of the detailed study we are completing on the z~2 ultra-luminous massive starburst galaxies selected by Spitzer in the mid-IR (24um-bright '5.8um-peakers'). Spitzer thus allows the selection of more than 100 z~1.5-2 ULIRGs per deg2, in ~70 deg2, with a far-IR luminosity approaching 10^13 Lsun/yr (SFR~1000 Msun/yr), including a large fraction of z~2 SMGs. Focussing on a complete sample in the 'Lockman-North' Field (0.5 deg2), we have shown their high detection rate at 1.2mm with MAMBO; checked their far-IR luminosity with 350um SHARC2/CSO observations and through the radio/far-IR correlation; studied in detail their prominent mid-IR PAH spectrum and checked its correlation with the far-IR emission; and begun their CO study. These sources are remarkably well detected by Herschel/SPIRE, even with the relatively shallow sensitivity of most HerMES widest fields. I will present a preliminary analysis of the far-IR emission of 5.8um-peakers in Lockman-SWIRE Field; its correlation with 24um emission; and the prospects that such sources offer for studying z~2 massive galaxies, their evolution, star formation and clustering.