Where do you draw the line?

I've struggled with a concept for such a long time.  It is the concept of money--where do you draw the line when you are purchasing something.  I am not attempting to write a sound theological argument or anything like that.  I am just putting my thoughts out there and seeing what kind of discussion I can generate.  Let me start off by giving an example of my struggle and then I can try to explain my thoughts.  Let's say you want to buy a car.  You can afford a new honda accord easily.  No sweat off your back, no debt.  Lets say this honda cost $25,000.  But someone asks you why you bought such an expensive car when you could have bought a used/new ________ (you fill in the blank for something cheaper).  Well, the first question is what is expensive?  I think expensive is a relative term.  If someone makes millions of dollars a 25,000 dollar car isn't much money at all.  Heck, 100,000 dollar car probably isn't much.  My question is for Christians though.  We are called to live above reproach.  Be different.  Have a higher standard for ourselves.  We are called to give to the needy, help the poor, etc.  Could I buy a cheaper car and give the difference to a family in need?  Yes, of course!  But, what if the new car I buy is safer than the used one.  What if the used one needs tons of repairs done on it?  What if the new one has a 5 year warranty.  For the sake of the argument, lets say you buy a cheaper car for $15,000.  That is a $10,000 difference.  But someone else says woah, why didn't you buy a 5,000 dollar car?  See what I am getting at?  Where do you draw the line?  Is it relative? You can always go cheaper so how cheap do you go?  I don't have the answers to this. I have struggled with this thought for a few years now and here are some of my thoughts so far are:

1.  Are you first of all giving you 10% to the church;

2.  Is it a need;

3.  Can something cheaper give you the same desired outcome without sacrificing safety (perhaps BMW vs. Honda);

4.  What is the Holy Spirit saying to you;

5.  What is your motivation for buying a "nicer" thing--recognition, pride, selfishness...;

6. When will enough be enough?  People always want more--faster, newer technologies, seat warmers/coolers, dvd players.  

I read through 1 Timothy today and the last chapter (6) is what finally sparked me to write about this struggle of mine.    

Starting in verse 6:

"But godliness with contentment is great gain.  For we brought nothing into the world, and we can take nothing out of it.  But if we have food and clothing, we will be content with that.  People who want to get rich fall into temptation and a trap and into many foolish and harmful desires that plunge men into ruin and destruction.  For the love of money is a root of all kinds of evil.  Some people, eager for money, have wandered from the faith and pierced themselves with many griefs."  

--FIrst of all, I don't want to fall into all that!  I am raising a child now and I want to raise her up in a way that will glorify the Lord.  She imitates EVERYTHING I do and I know it only gets worse. I am going to be held accountable for how I raised my children.  I want to be an example about how to spend wisely and I want to protect them from the things that happen when you desire riches.  I don't want to raise children who are selfish that think they need everything.  The Bible warns many times about the dangers of riches.  Plus, in my own life, i have seen it tear people down. 

--Continuing in the last section in chapter 6:17-19.

"Command those who are rich in this present world not to be arrogant nor to put their hope in wealth, which is so uncertain, but to put their hope in God, who richly provides us with everything for our enjoyment.  Command them to do good, to be rich in good deeds, and to be generous and willing to share.  In this age, so that they may take hold of the life that is truly life."

--Finally, I leave with this.  Some people are going to be rich and some will be poor.  No matter how much money is given, there are always going to be people in need.  Can we save them all (in regard to ridding the world of poverty, etc)?  No.  So, how much do we give?  How much do we sacrifice to help those in need?   Where do we draw the line?  

Thoughts?