Valuation is precisely what tells you how much the cash they have handed you is worth in terms of % in your company. If you negotiate the company is worth $500

Valuation is precisely what tells you how much the cash they have handed you is worth in terms of % in your company. If you negotiate the company is worth $500k rather than $225k, their $100k becomes 20% rather than 45%. You get the same cash, you've just diluted your company less, allowing more room for your series A, B, C and successive rounds. If you don't need the cash, are you trying to get an investment too early? Does $100k materially speed things up past your competition? If you've had two parties willing to invest already, would bootstrapping and building your valuation up put you in a stronger position? A few months building, getting more traction, establishing the business, working out monetization and getting a firmer plan of what you'll use the investment for might be a good 'breather'.