Ayuda a eleccion de makina!!!

Buenas a todos.
Tengo unas indecisiones tremendas ya que no se por donde empezar para elegir una bicicleta medio ké con un presupuesto máximo de 550 euros. Para empezar he sido aficionado toda mi vida pero ahora he decidido subirme de nuevo, pero me falta la montura y llevo varias semanas dando palos de ciego,¡SOIS MI ULTIMO CARTUCHOOO!!
Estoy entre varias marcas y sus respectivos modelos son:
1. Specialized Hardrock sport disc 2011 (HE ENCONTRADO LAS CARACTERISTICAS EN INGLES ESPERO QUE VALGAN)

FRAME Specialized A1 Premium Aluminum, fully butted, formed TT, Double ORE DT, externally relieved HT, reinforced disc mount, forged dropouts w/ replaceable hanger, disc only
REAR SHOCKFORKSR Suntour SF11-XCM-V3-26-DS-MLO, 80mm, 1pc. alloy lower, 30mm Hi-Ten stanchions, mechanical LO, coil/mcu spring w/ preload adj., spring assisted seals
HEADSET1-1/8" threadless, loose ball
STEM 3D forged alloy, 4 bolt, 10 degree rise, 25.4mm clamp
HANDLEBARS Alloy riserbar, 25mm rise, 8 degree back sweep, 6 degree up
GRIPS Specialized Enduro, dual compound Kraton, no flange, 131mm
FRONT BRAKE Avid BB5, mechanical disc, 160mm G2 Clean Sweep rotor
REAR BRAKE Avid BB5, mechanical disc, 160mm G2 Clean Sweep rotor
BRAKE LEVERS Alloy, linear pull
FRONT DERAILLEUR Shimano Altus, 34.9mm clamp
REAR DERAILLEUR Shimano Alivio, 9sp direct mount long cage
SHIFT LEVERS Shimano Acera SL, 8sp rapid fire trigger
CASSETTE SRAM PG-820, 8-speed, 11-32t
CHAIN KMC X8 w/ reuseable Missing Link
CRANKSET SR SunTour, Octalink spline
CHAINRINGS 42S x 32S x 22S replaceable
BOTTOM BRACKET Shimano BB-ES25, Octalink spline, cartridge bearing, 68mm x 118mm
PEDALS Composite platform, toe clip compatible, 9/16" w/ reflectors
RIMS Alex RHD 26", alloy double wall, pinned w/eyelets, 32h
FRONT HUB Forged alloy, hi/low flange, double sealed, ground race, machined disc mount and flange, QR, 32h
REAR HUB Forged alloy, mid flange, double sealed, ground race, machined disc mount and flanges, cassette, QR, 32h
SPOKES 2mm (14g) stainless
FRONT TIRE Specialized Fast Trak LK Sport, 26x2.0", 60TPI, wire bead
REAR TIRE Specialized Fast Trak LK Sport, 26x2.0", 60TPI, wire bead
INNER TUBES Schraeder valve
SADDLE Specialized XC, Body Geometry, 143mm width, front and rear bumpers
SEATPOST Alloy two bolt, 12.5mm offset, micro adjust, 30.9mm
SEAT BINDER Alloy QR, nylon washer
NOTES Chain stay protector, reflectors, clear coat, owners manual

GT AVALANCHE 2.0 DISC 2011

Brake Levers: Tektro
Rear Brake: Tektro Aquila cable actuated disc brake
Grips: GT Lockdown dual density with allen key fixing bolts
Handlebar: GT Mtn Riser, 15 mm rise, 6061 heat treated, 31.8 mm clamp
Headset: Tange Seiki system for 1 1/8"
Pedals: ATB Aluminum body, Steel cage, toe clip compatible
Rear Brake: Tektro Aquila cable actuated disc brake
Seat Clamp: GT Forged Alum QR
Seat Post: Alloy Micro adjust 31.6 mm
Stem: GT ATB, threadless 25 degree rise with four bolt alum CNC face plate for 31.8mm
Saddle: WTB Pure V, with stitched cover and protective corners
Bottom Bracket: Shimano Cartridge Sealed
Chain: HG 40 Shimano 8 speed Chain
Crankset Chainwheel: Shimano FC-M311 42/32/22
Front Derailleur: Shimano M -330
Rear Derailleur: Shimano Deore Shadow
Shifters: Shimano 8 speed rapidfire shifters
Fork: Suntour XCR-LO hydraulic fork with cr-mo 30 mm stanchions, magnesium lowers, preload adjust, 100 mm of travel and lock out
Frame: GT NEW Triple Triangle design 6061 butted aluminum with Hydro formed top and downtube, zero stack headtube. Disc compatible with removeable der. Hanger
Sizes: XXL,XL,L,M,S,XS
Front Hub: Alloy QR for Disc
Nipples: Brass CP
Rear Hub: Aluminum QR sealed mechanism 8 speed cassette for Disc
Rims: Jalco AX-430 Alloy double wall ATB
Spokes: Stainless steel 14 gauge
Tires: Kenda Nevegal, 26 x 2.1

TREK 4300 DISC:
Juego del cuadro
Tallas 13, 16, 18, 19.5, 21, 22.5, 24"
Cuadro: Alpha Black Aluminum w/semi-integrated head tube, formed down tube w/integrated gusset, formed top tube, monostay seatstay, forged dropouts w/rack & fender mounts, replaceable derailleur hanger
Suspensión Delantera: Spinner 300 w/coil spring, preload, hydraulic lockout, 100mm travel
Ruedas
Ruedas: Formula alloy DC20 front hub, Shimano alloy M475 rear hub; Bontrager Ranger 32-hole rims
Cubiertas: Bontrager XR2, wire bead, 26x2.1"
Transmisión
Manetas de Cambio: Shimano M360, 8 speed
Desviador: Shimano M310
Cambio: Shimano M410
Bielas: Shimano M311, 42/32/22
Cassette: SRAM PG-820 11-32, 8 speed
Pedales: Wellgo alloy platform
Componentes
Sillín: Bontrager Evoke 1
Tija de Sillín: Bontrager SSR, 31.6mm, 20mm offset
Manillar: Bontrager SSR, 25.4mm, 25mm rise
Potencia: Bontrager SSR, 25.4mm
Dirección: 1-1/8" threadless, semi-integrated, semi-cartridge bearings
Juego de Frenos: Promax DSK-907 hydraulic disc brakes

Esto es lo que he visto pero no tengo ni idea de lo que hacer. Se que todas esas marcas son buenas pero no se hasta que punto me las recomendais y si es asi cual de ellas.
Bueno ante todo, daros las gracias a todos aquellos que se molesten en leer esto y mas al que me eche una manilla es esto.
Un abrazo a todos.