Resistance training is the way to go. Add weight - get stronger. Simple as that. The Barbell is the bread-and-butter strength tool, tried and tested - nothing works better.
You don't necessarily need a bench, squat racks and any other equipment. With just a barbell you can do the following A - class strength exercises....
Deadlift - one of the all time great exercises Stiff legged Deadlift Romanian Deadlift Sumo Deadlift Overhead press - the old skool measure of strength Power Clean - classic lift for athletes needing speed-strength Push Press High Pull Snatch Pull Overhead squat - try this - it's an absolute killer Snatch - Karl Gotch likes this one Clean and Jerk Bent row Floor press - the old timers bench press Shrug Side Press Hack squat Zercher One arm deadlift Curl
...and that's just off the top of my head for starters, there's about 50 in The Weightlifting Encyclopedia...all of them are better strength builders than the fancy-pants machines in your local health club. And it won't cost you £60 a month membership either.
Also - if you get one at home you can do the Pavel Tsatsouline routine - just 2 sets of 2 exercises done with a barbell for "superstrength without bulk" Click for a review of Tsatsouline's Power to The People.
How much should you spend?
Now you could spend the price of a small car on barbells - check out the bars by Eleiko (a 132.5kg Eleiko set costs about $2500!) Leoko and Ivanko. Nope, that's no good. How about nipping down to your local Argos then? You can pick up at York Fitness 50kg set for $70. Yeah you can, but that's nowhere near heavy enough. Wrestling bears we said.
So do it right and get an Olympic barbell set. 140 kilos should keep you busy, that's 300 pounds and if you can hoist that overhead then people are probably very scared of you. The Bodypower Barbell set is the best value weight set I've seen to date.